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	$7.52	6.859%	$8.0358	$8.04	$8.05	$8.00
Purchase #2	$160.50	7.399%	$172.3754	$172.38	$172.40	$172.40
Purchase #3	$150.82	10.635%	$166.8597	$166.86	$166.85	$166.90
Purchase #4	$151.35	11.363%	$168.5479	$168.55	$168.55	$168.50
Purchase #5	$88.69	6.127%	$94.124	$94.12	$94.10	$94.10
Purchase #6	$208.26	11.634%	$232.489	$232.49	$232.50	$232.50
Purchase #7	$203.48	9.212%	$222.2246	$222.22	$222.20	$222.20
7 purchase totals =	$970.62		$1,064.6564	$1,064.66	$1,064.65	$1,064.60