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	$136.49	12.542%	$153.6086	$153.61	$153.60	$153.60
Purchase #2	$215.61	3.543%	$223.2491	$223.25	$223.25	$223.20
Purchase #3	$78.31	8.208%	$84.7377	$84.74	$84.75	$84.70
Purchase #4	$57.40	4.317%	$59.878	$59.88	$59.90	$59.90
Purchase #5	$204.90	13.686%	$232.9426	$232.94	$232.95	$232.90
Purchase #6	$63.50	6.522%	$67.6415	$67.64	$67.65	$67.60
Purchase #7	$52.29	9.686%	$57.3548	$57.35	$57.35	$57.40
7 purchase totals =	$808.50		$879.4123	$879.41	$879.45	$879.30