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	$137.82	5.846%	$145.877	$145.88	$145.90	$145.90
Purchase #2	$12.48	6.467%	$13.2871	$13.29	$13.30	$13.30
Purchase #3	$99.50	6.353%	$105.8212	$105.82	$105.80	$105.80
Purchase #4	$35.88	10.262%	$39.562	$39.56	$39.55	$39.60
Purchase #5	$159.28	6.294%	$169.3051	$169.31	$169.30	$169.30
Purchase #6	$242.77	10.345%	$267.8846	$267.88	$267.90	$267.90
Purchase #7	$249.97	5.762%	$264.3733	$264.37	$264.35	$264.40
7 purchase totals =	$937.70		$1,006.1103	$1,006.11	$1,006.10	$1,006.20