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	$203.94	6.319%	$216.827	$216.83	$216.85	$216.80
Purchase #2	$92.90	4.131%	$96.7377	$96.74	$96.75	$96.70
Purchase #3	$146.42	6.278%	$155.6122	$155.61	$155.60	$155.60
Purchase #4	$111.92	7.597%	$120.4226	$120.42	$120.40	$120.40
Purchase #5	$140.42	7.273%	$150.6327	$150.63	$150.65	$150.60
Purchase #6	$127.71	10.433%	$141.034	$141.03	$141.05	$141.00
Purchase #7	$113.83	12.716%	$128.3046	$128.30	$128.30	$128.30
7 purchase totals =	$937.14		$1,009.5708	$1,009.56	$1,009.60	$1,009.40