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	$61.33	5.268%	$64.5609	$64.56	$64.55	$64.60
Purchase #2	$68.37	5.161%	$71.8986	$71.90	$71.90	$71.90
Purchase #3	$233.49	11.285%	$259.8393	$259.84	$259.85	$259.80
Purchase #4	$146.35	9.386%	$160.0864	$160.09	$160.10	$160.10
Purchase #5	$235.31	6.446%	$250.4781	$250.48	$250.50	$250.50
Purchase #6	$233.77	10.825%	$259.0756	$259.08	$259.10	$259.10
Purchase #7	$221.76	3.639%	$229.8298	$229.83	$229.85	$229.80
7 purchase totals =	$1,200.38		$1,295.7687	$1,295.78	$1,295.85	$1,295.80