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	$32.66	11.465%	$36.4045	$36.40	$36.40	$36.40
Purchase #2	$101.83	3.226%	$105.115	$105.12	$105.10	$105.10
Purchase #3	$150.32	3.580%	$155.7015	$155.70	$155.70	$155.70
Purchase #4	$43.37	12.526%	$48.8025	$48.80	$48.80	$48.80
Purchase #5	$172.34	13.873%	$196.2487	$196.25	$196.25	$196.20
Purchase #6	$188.60	7.700%	$203.1222	$203.12	$203.10	$203.10
Purchase #7	$88.33	11.181%	$98.2062	$98.21	$98.20	$98.20
7 purchase totals =	$777.45		$843.6006	$843.60	$843.55	$843.50