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	$199.48	12.784%	$224.9815	$224.98	$225.00	$225.00
Purchase #2	$58.45	13.501%	$66.3413	$66.34	$66.35	$66.30
Purchase #3	$154.56	9.370%	$169.0423	$169.04	$169.05	$169.00
Purchase #4	$53.65	3.573%	$55.5669	$55.57	$55.55	$55.60
Purchase #5	$89.79	10.282%	$99.0222	$99.02	$99.00	$99.00
Purchase #6	$217.25	7.546%	$233.6437	$233.64	$233.65	$233.60
Purchase #7	$196.76	12.796%	$221.9374	$221.94	$221.95	$221.90
7 purchase totals =	$969.94		$1,070.5353	$1,070.53	$1,070.55	$1,070.40