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	$106.65	4.471%	$111.4183	$111.42	$111.40	$111.40
Purchase #2	$241.35	8.614%	$262.1399	$262.14	$262.15	$262.10
Purchase #3	$150.79	5.326%	$158.8211	$158.82	$158.80	$158.80
Purchase #4	$97.70	11.802%	$109.2306	$109.23	$109.25	$109.20
Purchase #5	$250.51	3.193%	$258.5088	$258.51	$258.50	$258.50
Purchase #6	$118.35	3.663%	$122.6852	$122.69	$122.70	$122.70
Purchase #7	$122.27	11.623%	$136.4814	$136.48	$136.50	$136.50
7 purchase totals =	$1,087.62		$1,159.2853	$1,159.29	$1,159.30	$1,159.20