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	$96.45	13.177%	$109.1592	$109.16	$109.15	$109.20
Purchase #2	$25.39	11.336%	$28.2682	$28.27	$28.25	$28.30
Purchase #3	$144.27	10.728%	$159.7473	$159.75	$159.75	$159.70
Purchase #4	$7.32	4.281%	$7.6334	$7.63	$7.65	$7.60
Purchase #5	$53.61	10.432%	$59.2026	$59.20	$59.20	$59.20
Purchase #6	$9.53	7.695%	$10.2633	$10.26	$10.25	$10.30
Purchase #7	$62.89	7.743%	$67.7596	$67.76	$67.75	$67.80
7 purchase totals =	$399.46		$442.0336	$442.03	$442.00	$442.10