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	$230.48	10.145%	$253.8622	$253.86	$253.85	$253.90
Purchase #2	$146.86	11.850%	$164.2629	$164.26	$164.25	$164.30
Purchase #3	$12.97	5.630%	$13.7002	$13.70	$13.70	$13.70
Purchase #4	$64.54	5.403%	$68.0271	$68.03	$68.05	$68.00
Purchase #5	$141.61	13.489%	$160.7118	$160.71	$160.70	$160.70
Purchase #6	$114.90	11.243%	$127.8182	$127.82	$127.80	$127.80
Purchase #7	$239.91	10.400%	$264.8606	$264.86	$264.85	$264.90
7 purchase totals =	$951.27		$1,053.2430	$1,053.24	$1,053.20	$1,053.30