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	$239.41	7.123%	$256.4632	$256.46	$256.45	$256.50
Purchase #2	$42.98	13.274%	$48.6852	$48.69	$48.70	$48.70
Purchase #3	$73.92	7.205%	$79.2459	$79.25	$79.25	$79.20
Purchase #4	$111.33	11.801%	$124.4681	$124.47	$124.45	$124.50
Purchase #5	$58.97	4.183%	$61.4367	$61.44	$61.45	$61.40
Purchase #6	$25.45	7.132%	$27.2651	$27.27	$27.25	$27.30
Purchase #7	$30.84	5.481%	$32.5303	$32.53	$32.55	$32.50
7 purchase totals =	$582.90		$630.0945	$630.11	$630.10	$630.10