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	$186.62	5.210%	$196.3429	$196.34	$196.35	$196.30
Purchase #2	$131.75	12.507%	$148.228	$148.23	$148.25	$148.20
Purchase #3	$131.73	12.560%	$148.2753	$148.28	$148.30	$148.30
Purchase #4	$228.99	10.508%	$253.0523	$253.05	$253.05	$253.10
Purchase #5	$201.63	11.303%	$224.4202	$224.42	$224.40	$224.40
Purchase #6	$228.87	12.798%	$258.1608	$258.16	$258.15	$258.20
Purchase #7	$56.74	4.382%	$59.2263	$59.23	$59.25	$59.20
7 purchase totals =	$1,166.33		$1,287.7058	$1,287.71	$1,287.75	$1,287.70