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	$130.44	10.669%	$144.3566	$144.36	$144.35	$144.40
Purchase #2	$129.71	10.438%	$143.2491	$143.25	$143.25	$143.20
Purchase #3	$54.87	11.121%	$60.9721	$60.97	$60.95	$61.00
Purchase #4	$38.93	12.572%	$43.8243	$43.82	$43.80	$43.80
Purchase #5	$67.54	6.290%	$71.7883	$71.79	$71.80	$71.80
Purchase #6	$126.38	11.873%	$141.3851	$141.39	$141.40	$141.40
Purchase #7	$93.80	6.654%	$100.0415	$100.04	$100.05	$100.00
7 purchase totals =	$641.67		$705.6170	$705.62	$705.60	$705.60