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	$168.77	13.270%	$191.1658	$191.17	$191.15	$191.20
Purchase #2	$100.38	3.110%	$103.5018	$103.50	$103.50	$103.50
Purchase #3	$200.54	7.673%	$215.9274	$215.93	$215.95	$215.90
Purchase #4	$77.63	8.433%	$84.1765	$84.18	$84.20	$84.20
Purchase #5	$37.57	7.550%	$40.4065	$40.41	$40.40	$40.40
Purchase #6	$86.46	3.267%	$89.2846	$89.28	$89.30	$89.30
Purchase #7	$108.94	12.306%	$122.3462	$122.35	$122.35	$122.30
7 purchase totals =	$780.29		$846.8088	$846.82	$846.85	$846.80