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	$88.96	8.113%	$96.1773	$96.18	$96.20	$96.20
Purchase #2	$12.85	6.669%	$13.707	$13.71	$13.70	$13.70
Purchase #3	$51.28	12.750%	$57.8182	$57.82	$57.80	$57.80
Purchase #4	$18.46	12.264%	$20.7239	$20.72	$20.70	$20.70
Purchase #5	$126.27	12.438%	$141.9755	$141.98	$142.00	$142.00
Purchase #6	$56.61	4.732%	$59.2888	$59.29	$59.30	$59.30
Purchase #7	$216.37	4.267%	$225.6025	$225.60	$225.60	$225.60
7 purchase totals =	$570.80		$615.2932	$615.30	$615.30	$615.30