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	$58.64	10.121%	$64.575	$64.58	$64.60	$64.60
Purchase #2	$53.71	13.725%	$61.0817	$61.08	$61.10	$61.10
Purchase #3	$48.53	6.690%	$51.7767	$51.78	$51.80	$51.80
Purchase #4	$170.60	8.689%	$185.4234	$185.42	$185.40	$185.40
Purchase #5	$70.43	7.855%	$75.9623	$75.96	$75.95	$76.00
Purchase #6	$176.46	11.152%	$196.1388	$196.14	$196.15	$196.10
Purchase #7	$63.90	11.290%	$71.1143	$71.11	$71.10	$71.10
7 purchase totals =	$642.27		$706.0722	$706.07	$706.10	$706.10