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	$99.56	8.240%	$107.7637	$107.76	$107.75	$107.80
Purchase #2	$40.98	3.712%	$42.5012	$42.50	$42.50	$42.50
Purchase #3	$54.80	12.868%	$61.8517	$61.85	$61.85	$61.90
Purchase #4	$93.57	8.496%	$101.5197	$101.52	$101.50	$101.50
Purchase #5	$130.83	13.136%	$148.0158	$148.02	$148.00	$148.00
Purchase #6	$159.29	6.667%	$169.9099	$169.91	$169.90	$169.90
Purchase #7	$106.51	9.830%	$116.9799	$116.98	$117.00	$117.00
7 purchase totals =	$685.54		$748.5419	$748.54	$748.50	$748.60