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	$96.40	13.254%	$109.1769	$109.18	$109.20	$109.20
Purchase #2	$141.42	4.576%	$147.8914	$147.89	$147.90	$147.90
Purchase #3	$179.90	6.145%	$190.9549	$190.95	$190.95	$191.00
Purchase #4	$181.78	5.651%	$192.0524	$192.05	$192.05	$192.10
Purchase #5	$220.38	4.619%	$230.5594	$230.56	$230.55	$230.60
Purchase #6	$54.29	13.168%	$61.4389	$61.44	$61.45	$61.40
Purchase #7	$134.75	11.790%	$150.637	$150.64	$150.65	$150.60
7 purchase totals =	$1,008.92		$1,082.7109	$1,082.71	$1,082.75	$1,082.80