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	$25.58	8.650%	$27.7927	$27.79	$27.80	$27.80
Purchase #2	$243.35	4.263%	$253.724	$253.72	$253.70	$253.70
Purchase #3	$226.33	3.795%	$234.9192	$234.92	$234.90	$234.90
Purchase #4	$47.27	10.806%	$52.378	$52.38	$52.40	$52.40
Purchase #5	$179.42	9.388%	$196.2639	$196.26	$196.25	$196.30
Purchase #6	$87.50	13.220%	$99.0675	$99.07	$99.05	$99.10
Purchase #7	$141.93	7.363%	$152.3803	$152.38	$152.40	$152.40
7 purchase totals =	$951.38		$1,016.5256	$1,016.52	$1,016.50	$1,016.60