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	$119.45	4.552%	$124.8874	$124.89	$124.90	$124.90
Purchase #2	$242.45	8.376%	$262.7576	$262.76	$262.75	$262.80
Purchase #3	$232.44	9.457%	$254.4219	$254.42	$254.40	$254.40
Purchase #4	$173.45	11.792%	$193.9032	$193.90	$193.90	$193.90
Purchase #5	$80.95	10.347%	$89.3259	$89.33	$89.35	$89.30
Purchase #6	$224.31	8.718%	$243.8653	$243.87	$243.85	$243.90
Purchase #7	$41.47	11.702%	$46.3228	$46.32	$46.30	$46.30
7 purchase totals =	$1,114.52		$1,215.4841	$1,215.49	$1,215.45	$1,215.50