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	$183.52	6.830%	$196.0544	$196.05	$196.05	$196.10
Purchase #2	$82.26	9.323%	$89.9291	$89.93	$89.95	$89.90
Purchase #3	$189.90	6.337%	$201.934	$201.93	$201.95	$201.90
Purchase #4	$147.33	12.474%	$165.7079	$165.71	$165.70	$165.70
Purchase #5	$243.63	8.743%	$264.9306	$264.93	$264.95	$264.90
Purchase #6	$194.68	11.516%	$217.0993	$217.10	$217.10	$217.10
Purchase #7	$176.75	11.182%	$196.5142	$196.51	$196.50	$196.50
7 purchase totals =	$1,218.07		$1,332.1695	$1,332.16	$1,332.20	$1,332.10