Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.88	10.502%	$111.4744	$111.47	$111.45	$111.50
Purchase #2	$215.80	13.581%	$245.1078	$245.11	$245.10	$245.10
Purchase #3	$95.44	11.411%	$106.3307	$106.33	$106.35	$106.30
Purchase #4	$228.78	12.293%	$256.9039	$256.90	$256.90	$256.90
Purchase #5	$177.57	12.597%	$199.9385	$199.94	$199.95	$199.90
Purchase #6	$245.92	11.535%	$274.2869	$274.29	$274.30	$274.30
Purchase #7	$194.51	12.168%	$218.178	$218.18	$218.20	$218.20
7 purchase totals =	$1,258.90		$1,412.2202	$1,412.22	$1,412.25	$1,412.20