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	$136.78	11.482%	$152.4851	$152.49	$152.50	$152.50
Purchase #2	$103.78	12.148%	$116.3872	$116.39	$116.40	$116.40
Purchase #3	$115.38	11.707%	$128.8875	$128.89	$128.90	$128.90
Purchase #4	$88.58	7.864%	$95.5459	$95.55	$95.55	$95.50
Purchase #5	$154.44	9.648%	$169.3404	$169.34	$169.35	$169.30
Purchase #6	$135.32	9.335%	$147.9521	$147.95	$147.95	$148.00
Purchase #7	$246.51	5.705%	$260.5734	$260.57	$260.55	$260.60
7 purchase totals =	$980.79		$1,071.1716	$1,071.18	$1,071.20	$1,071.20