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	$84.41	9.385%	$92.3319	$92.33	$92.35	$92.30
Purchase #2	$101.46	5.339%	$106.8769	$106.88	$106.90	$106.90
Purchase #3	$135.83	5.522%	$143.3305	$143.33	$143.35	$143.30
Purchase #4	$180.66	7.679%	$194.5329	$194.53	$194.55	$194.50
Purchase #5	$42.88	5.439%	$45.2122	$45.21	$45.20	$45.20
Purchase #6	$149.42	13.419%	$169.4707	$169.47	$169.45	$169.50
Purchase #7	$244.30	8.265%	$264.4914	$264.49	$264.50	$264.50
7 purchase totals =	$938.96		$1,016.2465	$1,016.24	$1,016.30	$1,016.20