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	$236.50	4.753%	$247.7408	$247.74	$247.75	$247.70
Purchase #2	$94.88	11.308%	$105.609	$105.61	$105.60	$105.60
Purchase #3	$244.49	4.562%	$255.6436	$255.64	$255.65	$255.60
Purchase #4	$82.54	13.833%	$93.9578	$93.96	$93.95	$94.00
Purchase #5	$94.65	5.144%	$99.5188	$99.52	$99.50	$99.50
Purchase #6	$228.37	5.759%	$241.5218	$241.52	$241.50	$241.50
Purchase #7	$89.48	10.686%	$99.0418	$99.04	$99.05	$99.00
7 purchase totals =	$1,070.91		$1,143.0336	$1,143.03	$1,143.00	$1,142.90