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	$141.83	9.573%	$155.4074	$155.41	$155.40	$155.40
Purchase #2	$213.39	4.189%	$222.3289	$222.33	$222.35	$222.30
Purchase #3	$224.89	3.745%	$233.3121	$233.31	$233.30	$233.30
Purchase #4	$169.58	4.240%	$176.7702	$176.77	$176.75	$176.80
Purchase #5	$55.83	6.582%	$59.5047	$59.50	$59.50	$59.50
Purchase #6	$33.58	9.441%	$36.7503	$36.75	$36.75	$36.80
Purchase #7	$239.58	3.528%	$248.0324	$248.03	$248.05	$248.00
7 purchase totals =	$1,078.68		$1,132.1060	$1,132.10	$1,132.10	$1,132.10