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	$34.68	4.706%	$36.312	$36.31	$36.30	$36.30
Purchase #2	$100.91	11.196%	$112.2079	$112.21	$112.20	$112.20
Purchase #3	$25.42	7.363%	$27.2917	$27.29	$27.30	$27.30
Purchase #4	$211.76	3.837%	$219.8852	$219.89	$219.90	$219.90
Purchase #5	$56.87	3.820%	$59.0424	$59.04	$59.05	$59.00
Purchase #6	$238.99	11.122%	$265.5705	$265.57	$265.55	$265.60
Purchase #7	$6.87	8.551%	$7.4575	$7.46	$7.45	$7.50
7 purchase totals =	$675.50		$727.7672	$727.77	$727.75	$727.80