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	$117.57	6.462%	$125.1674	$125.17	$125.15	$125.20
Purchase #2	$222.97	6.175%	$236.7384	$236.74	$236.75	$236.70
Purchase #3	$229.70	8.352%	$248.8845	$248.88	$248.90	$248.90
Purchase #4	$83.30	7.700%	$89.7141	$89.71	$89.70	$89.70
Purchase #5	$39.44	4.250%	$41.1162	$41.12	$41.10	$41.10
Purchase #6	$218.84	3.221%	$225.8888	$225.89	$225.90	$225.90
Purchase #7	$168.35	10.420%	$185.8921	$185.89	$185.90	$185.90
7 purchase totals =	$1,080.17		$1,153.4015	$1,153.40	$1,153.40	$1,153.40