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	$42.81	7.125%	$45.8602	$45.86	$45.85	$45.90
Purchase #2	$203.57	3.478%	$210.6502	$210.65	$210.65	$210.70
Purchase #3	$141.47	6.640%	$150.8636	$150.86	$150.85	$150.90
Purchase #4	$99.44	5.799%	$105.2065	$105.21	$105.20	$105.20
Purchase #5	$59.62	10.153%	$65.6732	$65.67	$65.65	$65.70
Purchase #6	$141.41	7.406%	$151.8828	$151.88	$151.90	$151.90
Purchase #7	$139.57	11.347%	$155.407	$155.41	$155.40	$155.40
7 purchase totals =	$827.89		$885.5435	$885.54	$885.50	$885.70