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	$96.49	8.731%	$104.9145	$104.91	$104.90	$104.90
Purchase #2	$100.32	8.427%	$108.774	$108.77	$108.75	$108.80
Purchase #3	$139.36	3.770%	$144.6139	$144.61	$144.60	$144.60
Purchase #4	$43.56	13.625%	$49.4951	$49.50	$49.50	$49.50
Purchase #5	$233.47	4.191%	$243.2547	$243.25	$243.25	$243.30
Purchase #6	$86.70	4.723%	$90.7948	$90.79	$90.80	$90.80
Purchase #7	$238.52	6.635%	$254.3458	$254.35	$254.35	$254.30
7 purchase totals =	$938.42		$996.1928	$996.18	$996.15	$996.20