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	$93.66	12.257%	$105.1399	$105.14	$105.15	$105.10
Purchase #2	$147.87	5.641%	$156.2113	$156.21	$156.20	$156.20
Purchase #3	$79.32	7.678%	$85.4102	$85.41	$85.40	$85.40
Purchase #4	$9.73	11.176%	$10.8174	$10.82	$10.80	$10.80
Purchase #5	$151.82	8.798%	$165.1771	$165.18	$165.20	$165.20
Purchase #6	$181.47	10.525%	$200.5697	$200.57	$200.55	$200.60
Purchase #7	$60.46	7.180%	$64.801	$64.80	$64.80	$64.80
7 purchase totals =	$724.33		$788.1266	$788.13	$788.10	$788.10