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	$39.82	4.606%	$41.6541	$41.65	$41.65	$41.70
Purchase #2	$149.67	8.678%	$162.6584	$162.66	$162.65	$162.70
Purchase #3	$76.79	9.111%	$83.7863	$83.79	$83.80	$83.80
Purchase #4	$68.83	12.135%	$77.1825	$77.18	$77.20	$77.20
Purchase #5	$99.91	11.815%	$111.7144	$111.71	$111.70	$111.70
Purchase #6	$97.91	11.690%	$109.3557	$109.36	$109.35	$109.40
Purchase #7	$153.72	7.731%	$165.6041	$165.60	$165.60	$165.60
7 purchase totals =	$686.65		$751.9555	$751.95	$751.95	$752.10