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	$75.70	12.130%	$84.8824	$84.88	$84.90	$84.90
Purchase #2	$27.83	13.215%	$31.5077	$31.51	$31.50	$31.50
Purchase #3	$224.31	11.851%	$250.893	$250.89	$250.90	$250.90
Purchase #4	$31.81	6.175%	$33.7743	$33.77	$33.75	$33.80
Purchase #5	$148.33	4.736%	$155.3549	$155.35	$155.35	$155.40
Purchase #6	$170.52	4.472%	$178.1457	$178.15	$178.15	$178.10
Purchase #7	$198.44	4.298%	$206.969	$206.97	$206.95	$207.00
7 purchase totals =	$876.94		$941.5270	$941.52	$941.50	$941.60