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	$224.34	12.811%	$253.0802	$253.08	$253.10	$253.10
Purchase #2	$55.32	13.460%	$62.7661	$62.77	$62.75	$62.80
Purchase #3	$139.90	4.685%	$146.4543	$146.45	$146.45	$146.50
Purchase #4	$43.95	9.317%	$48.0448	$48.04	$48.05	$48.00
Purchase #5	$243.44	11.206%	$270.7199	$270.72	$270.70	$270.70
Purchase #6	$103.61	7.279%	$111.1518	$111.15	$111.15	$111.20
Purchase #7	$199.48	6.785%	$213.0147	$213.01	$213.00	$213.00
7 purchase totals =	$1,010.04		$1,105.2318	$1,105.22	$1,105.20	$1,105.30