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	$55.74	6.498%	$59.362	$59.36	$59.35	$59.40
Purchase #2	$83.31	11.453%	$92.8515	$92.85	$92.85	$92.90
Purchase #3	$140.97	3.769%	$146.2832	$146.28	$146.30	$146.30
Purchase #4	$88.42	3.705%	$91.696	$91.70	$91.70	$91.70
Purchase #5	$141.84	11.362%	$157.9559	$157.96	$157.95	$158.00
Purchase #6	$135.61	7.136%	$145.2871	$145.29	$145.30	$145.30
Purchase #7	$31.55	7.319%	$33.8591	$33.86	$33.85	$33.90
7 purchase totals =	$677.44		$727.2948	$727.30	$727.30	$727.50