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	$227.87	11.768%	$254.6857	$254.69	$254.70	$254.70
Purchase #2	$79.59	12.671%	$89.6748	$89.67	$89.65	$89.70
Purchase #3	$240.48	10.192%	$264.9897	$264.99	$265.00	$265.00
Purchase #4	$98.98	12.352%	$111.206	$111.21	$111.20	$111.20
Purchase #5	$126.92	5.847%	$134.341	$134.34	$134.35	$134.30
Purchase #6	$129.63	7.423%	$139.2524	$139.25	$139.25	$139.30
Purchase #7	$156.65	10.160%	$172.5656	$172.57	$172.55	$172.60
7 purchase totals =	$1,060.12		$1,166.7152	$1,166.72	$1,166.70	$1,166.80