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	$165.32	9.753%	$181.4437	$181.44	$181.45	$181.40
Purchase #2	$33.26	12.431%	$37.3946	$37.39	$37.40	$37.40
Purchase #3	$59.82	4.562%	$62.549	$62.55	$62.55	$62.50
Purchase #4	$33.62	12.627%	$37.8652	$37.87	$37.85	$37.90
Purchase #5	$172.92	8.425%	$187.4885	$187.49	$187.50	$187.50
Purchase #6	$114.80	12.190%	$128.7941	$128.79	$128.80	$128.80
Purchase #7	$22.83	10.679%	$25.268	$25.27	$25.25	$25.30
7 purchase totals =	$602.57		$660.8031	$660.80	$660.80	$660.80