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	$218.63	10.802%	$242.2464	$242.25	$242.25	$242.20
Purchase #2	$206.31	6.715%	$220.1637	$220.16	$220.15	$220.20
Purchase #3	$152.49	6.591%	$162.5406	$162.54	$162.55	$162.50
Purchase #4	$95.81	4.793%	$100.4022	$100.40	$100.40	$100.40
Purchase #5	$95.59	13.737%	$108.7212	$108.72	$108.70	$108.70
Purchase #6	$27.54	9.567%	$30.1748	$30.17	$30.15	$30.20
Purchase #7	$30.34	4.543%	$31.7183	$31.72	$31.70	$31.70
7 purchase totals =	$826.71		$895.9672	$895.96	$895.90	$895.90