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	$67.64	12.361%	$76.001	$76.00	$76.00	$76.00
Purchase #2	$128.76	4.315%	$134.316	$134.32	$134.30	$134.30
Purchase #3	$167.27	13.760%	$190.2864	$190.29	$190.30	$190.30
Purchase #4	$111.51	10.583%	$123.3111	$123.31	$123.30	$123.30
Purchase #5	$72.50	13.799%	$82.5043	$82.50	$82.50	$82.50
Purchase #6	$59.68	5.158%	$62.7583	$62.76	$62.75	$62.80
Purchase #7	$234.57	4.116%	$244.2249	$244.22	$244.20	$244.20
7 purchase totals =	$841.93		$913.4020	$913.40	$913.35	$913.40