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	$31.41	4.740%	$32.8988	$32.90	$32.90	$32.90
Purchase #2	$180.58	7.694%	$194.4738	$194.47	$194.45	$194.50
Purchase #3	$192.59	11.501%	$214.7398	$214.74	$214.75	$214.70
Purchase #4	$208.50	13.493%	$236.6329	$236.63	$236.65	$236.60
Purchase #5	$162.45	10.327%	$179.2262	$179.23	$179.25	$179.20
Purchase #6	$89.67	10.689%	$99.2548	$99.25	$99.25	$99.30
Purchase #7	$92.29	11.251%	$102.6735	$102.67	$102.65	$102.70
7 purchase totals =	$957.49		$1,059.8998	$1,059.89	$1,059.90	$1,059.90