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	$100.35	5.557%	$105.9264	$105.93	$105.95	$105.90
Purchase #2	$18.32	5.151%	$19.2637	$19.26	$19.25	$19.30
Purchase #3	$43.37	6.865%	$46.3474	$46.35	$46.35	$46.30
Purchase #4	$119.37	7.755%	$128.6271	$128.63	$128.65	$128.60
Purchase #5	$37.81	9.588%	$41.4352	$41.44	$41.45	$41.40
Purchase #6	$128.65	11.420%	$143.3418	$143.34	$143.35	$143.30
Purchase #7	$62.60	13.742%	$71.2025	$71.20	$71.20	$71.20
7 purchase totals =	$510.47		$556.1441	$556.15	$556.20	$556.00