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	$119.74	9.258%	$130.8255	$130.83	$130.85	$130.80
Purchase #2	$104.58	7.239%	$112.1505	$112.15	$112.15	$112.20
Purchase #3	$24.29	12.265%	$27.2692	$27.27	$27.25	$27.30
Purchase #4	$32.96	9.698%	$36.1565	$36.16	$36.15	$36.20
Purchase #5	$141.33	7.697%	$152.2082	$152.21	$152.20	$152.20
Purchase #6	$49.63	9.810%	$54.4987	$54.50	$54.50	$54.50
Purchase #7	$65.69	8.588%	$71.3315	$71.33	$71.35	$71.30
7 purchase totals =	$538.22		$584.4401	$584.45	$584.45	$584.50