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	$212.48	4.591%	$222.235	$222.24	$222.25	$222.20
Purchase #2	$48.63	3.674%	$50.4167	$50.42	$50.40	$50.40
Purchase #3	$209.34	11.328%	$233.054	$233.05	$233.05	$233.10
Purchase #4	$65.37	3.699%	$67.788	$67.79	$67.80	$67.80
Purchase #5	$130.70	7.121%	$140.0071	$140.01	$140.00	$140.00
Purchase #6	$184.54	8.381%	$200.0063	$200.01	$200.00	$200.00
Purchase #7	$227.46	4.654%	$238.046	$238.05	$238.05	$238.00
7 purchase totals =	$1,078.52		$1,151.5531	$1,151.57	$1,151.55	$1,151.50