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	$40.56	4.175%	$42.2534	$42.25	$42.25	$42.30
Purchase #2	$217.48	13.824%	$247.5444	$247.54	$247.55	$247.50
Purchase #3	$195.83	5.270%	$206.1502	$206.15	$206.15	$206.20
Purchase #4	$197.71	13.537%	$224.474	$224.47	$224.45	$224.50
Purchase #5	$151.33	11.234%	$168.3304	$168.33	$168.35	$168.30
Purchase #6	$49.93	13.688%	$56.7644	$56.76	$56.75	$56.80
Purchase #7	$166.48	10.868%	$184.573	$184.57	$184.55	$184.60
7 purchase totals =	$1,019.32		$1,130.0898	$1,130.07	$1,130.05	$1,130.20