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	$86.89	7.213%	$93.1574	$93.16	$93.15	$93.20
Purchase #2	$86.34	5.715%	$91.2743	$91.27	$91.25	$91.30
Purchase #3	$19.90	9.240%	$21.7388	$21.74	$21.75	$21.70
Purchase #4	$13.89	9.465%	$15.2047	$15.20	$15.20	$15.20
Purchase #5	$95.87	8.824%	$104.3296	$104.33	$104.35	$104.30
Purchase #6	$50.54	9.362%	$55.2716	$55.27	$55.25	$55.30
Purchase #7	$69.50	3.426%	$71.8811	$71.88	$71.90	$71.90
7 purchase totals =	$422.93		$452.8575	$452.85	$452.85	$452.90