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	$250.27	7.576%	$269.2305	$269.23	$269.25	$269.20
Purchase #2	$29.68	10.335%	$32.7474	$32.75	$32.75	$32.70
Purchase #3	$199.28	11.696%	$222.5878	$222.59	$222.60	$222.60
Purchase #4	$181.35	10.743%	$200.8324	$200.83	$200.85	$200.80
Purchase #5	$136.73	12.359%	$153.6285	$153.63	$153.65	$153.60
Purchase #6	$84.61	5.811%	$89.5267	$89.53	$89.55	$89.50
Purchase #7	$204.62	7.304%	$219.5654	$219.57	$219.55	$219.60
7 purchase totals =	$1,086.54		$1,188.1187	$1,188.13	$1,188.20	$1,188.00