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	$17.44	3.691%	$18.0837	$18.08	$18.10	$18.10
Purchase #2	$10.34	10.511%	$11.4268	$11.43	$11.45	$11.40
Purchase #3	$212.83	4.481%	$222.3669	$222.37	$222.35	$222.40
Purchase #4	$146.73	13.756%	$166.9142	$166.91	$166.90	$166.90
Purchase #5	$38.76	13.155%	$43.8589	$43.86	$43.85	$43.90
Purchase #6	$186.98	13.680%	$212.5589	$212.56	$212.55	$212.60
Purchase #7	$58.43	12.160%	$65.5351	$65.54	$65.55	$65.50
7 purchase totals =	$671.51		$740.7445	$740.75	$740.75	$740.80