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	$29.30	11.294%	$32.6091	$32.61	$32.60	$32.60
Purchase #2	$100.90	10.461%	$111.4551	$111.46	$111.45	$111.50
Purchase #3	$32.71	11.190%	$36.3702	$36.37	$36.35	$36.40
Purchase #4	$159.38	12.657%	$179.5527	$179.55	$179.55	$179.60
Purchase #5	$250.51	11.177%	$278.5095	$278.51	$278.50	$278.50
Purchase #6	$207.54	11.837%	$232.1065	$232.11	$232.10	$232.10
Purchase #7	$159.33	13.115%	$180.2261	$180.23	$180.25	$180.20
7 purchase totals =	$939.67		$1,050.8292	$1,050.84	$1,050.80	$1,050.90