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	$242.83	3.211%	$250.6273	$250.63	$250.65	$250.60
Purchase #2	$154.63	11.869%	$172.983	$172.98	$173.00	$173.00
Purchase #3	$191.40	7.666%	$206.0727	$206.07	$206.05	$206.10
Purchase #4	$178.93	6.456%	$190.4817	$190.48	$190.50	$190.50
Purchase #5	$202.85	9.532%	$222.1857	$222.19	$222.20	$222.20
Purchase #6	$160.47	7.514%	$172.5277	$172.53	$172.55	$172.50
Purchase #7	$117.58	8.231%	$127.258	$127.26	$127.25	$127.30
7 purchase totals =	$1,248.69		$1,342.1361	$1,342.14	$1,342.20	$1,342.20