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	$204.97	5.557%	$216.3602	$216.36	$216.35	$216.40
Purchase #2	$165.85	7.760%	$178.72	$178.72	$178.70	$178.70
Purchase #3	$122.61	7.642%	$131.9799	$131.98	$132.00	$132.00
Purchase #4	$10.73	10.376%	$11.8433	$11.84	$11.85	$11.80
Purchase #5	$139.95	4.758%	$146.6088	$146.61	$146.60	$146.60
Purchase #6	$198.89	6.812%	$212.4384	$212.44	$212.45	$212.40
Purchase #7	$197.54	12.706%	$222.6394	$222.64	$222.65	$222.60
7 purchase totals =	$1,040.54		$1,120.5900	$1,120.59	$1,120.60	$1,120.50