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	$155.57	11.605%	$173.6239	$173.62	$173.60	$173.60
Purchase #2	$90.96	10.185%	$100.2243	$100.22	$100.20	$100.20
Purchase #3	$174.30	12.322%	$195.7772	$195.78	$195.80	$195.80
Purchase #4	$86.30	11.180%	$95.9483	$95.95	$95.95	$95.90
Purchase #5	$154.75	6.865%	$165.3736	$165.37	$165.35	$165.40
Purchase #6	$81.38	7.490%	$87.4754	$87.48	$87.50	$87.50
Purchase #7	$179.25	12.363%	$201.4107	$201.41	$201.40	$201.40
7 purchase totals =	$922.51		$1,019.8334	$1,019.83	$1,019.80	$1,019.80