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	$165.73	7.122%	$177.5333	$177.53	$177.55	$177.50
Purchase #2	$110.56	11.317%	$123.0721	$123.07	$123.05	$123.10
Purchase #3	$145.77	13.126%	$164.9038	$164.90	$164.90	$164.90
Purchase #4	$53.70	10.695%	$59.4432	$59.44	$59.45	$59.40
Purchase #5	$231.77	13.811%	$263.7798	$263.78	$263.80	$263.80
Purchase #6	$65.74	13.453%	$74.584	$74.58	$74.60	$74.60
Purchase #7	$202.85	5.780%	$214.5747	$214.57	$214.55	$214.60
7 purchase totals =	$976.12		$1,077.8909	$1,077.87	$1,077.90	$1,077.90