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	$132.75	11.301%	$147.7521	$147.75	$147.75	$147.80
Purchase #2	$99.58	11.599%	$111.1303	$111.13	$111.15	$111.10
Purchase #3	$109.79	7.616%	$118.1516	$118.15	$118.15	$118.20
Purchase #4	$241.36	6.181%	$256.2785	$256.28	$256.30	$256.30
Purchase #5	$170.34	9.857%	$187.1304	$187.13	$187.15	$187.10
Purchase #6	$223.96	4.814%	$234.7414	$234.74	$234.75	$234.70
Purchase #7	$44.56	8.346%	$48.279	$48.28	$48.30	$48.30
7 purchase totals =	$1,022.34		$1,103.4633	$1,103.46	$1,103.55	$1,103.50