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	$175.51	5.320%	$184.8471	$184.85	$184.85	$184.80
Purchase #2	$78.69	13.147%	$89.0354	$89.04	$89.05	$89.00
Purchase #3	$70.43	7.785%	$75.913	$75.91	$75.90	$75.90
Purchase #4	$67.95	5.701%	$71.8238	$71.82	$71.80	$71.80
Purchase #5	$39.54	9.487%	$43.2912	$43.29	$43.30	$43.30
Purchase #6	$58.35	7.529%	$62.7432	$62.74	$62.75	$62.70
Purchase #7	$229.60	12.847%	$259.0967	$259.10	$259.10	$259.10
7 purchase totals =	$720.07		$786.7504	$786.75	$786.75	$786.60