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	$57.72	11.674%	$64.4582	$64.46	$64.45	$64.50
Purchase #2	$79.33	13.131%	$89.7468	$89.75	$89.75	$89.70
Purchase #3	$230.48	10.543%	$254.7795	$254.78	$254.80	$254.80
Purchase #4	$119.37	10.787%	$132.2464	$132.25	$132.25	$132.20
Purchase #5	$168.31	10.266%	$185.5887	$185.59	$185.60	$185.60
Purchase #6	$231.31	10.111%	$254.6978	$254.70	$254.70	$254.70
Purchase #7	$125.62	3.420%	$129.9162	$129.92	$129.90	$129.90
7 purchase totals =	$1,012.14		$1,111.4336	$1,111.45	$1,111.45	$1,111.40