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	$245.62	3.136%	$253.3226	$253.32	$253.30	$253.30
Purchase #2	$40.89	12.588%	$46.0372	$46.04	$46.05	$46.00
Purchase #3	$70.30	6.518%	$74.8822	$74.88	$74.90	$74.90
Purchase #4	$239.82	7.102%	$256.852	$256.85	$256.85	$256.90
Purchase #5	$82.93	5.282%	$87.3104	$87.31	$87.30	$87.30
Purchase #6	$98.76	13.835%	$112.4234	$112.42	$112.40	$112.40
Purchase #7	$225.69	13.673%	$256.5486	$256.55	$256.55	$256.50
7 purchase totals =	$1,004.01		$1,087.3764	$1,087.37	$1,087.35	$1,087.30