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	$98.79	4.388%	$103.1249	$103.12	$103.10	$103.10
Purchase #2	$147.44	5.432%	$155.4489	$155.45	$155.45	$155.40
Purchase #3	$247.77	12.158%	$277.8939	$277.89	$277.90	$277.90
Purchase #4	$107.52	4.846%	$112.7304	$112.73	$112.75	$112.70
Purchase #5	$200.27	11.296%	$222.8925	$222.89	$222.90	$222.90
Purchase #6	$244.77	13.319%	$277.3709	$277.37	$277.35	$277.40
Purchase #7	$24.98	8.491%	$27.1011	$27.10	$27.10	$27.10
7 purchase totals =	$1,071.54		$1,176.5626	$1,176.55	$1,176.55	$1,176.50