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	$74.95	10.302%	$82.6713	$82.67	$82.65	$82.70
Purchase #2	$123.79	10.859%	$137.2324	$137.23	$137.25	$137.20
Purchase #3	$63.84	9.392%	$69.8359	$69.84	$69.85	$69.80
Purchase #4	$12.68	6.188%	$13.4646	$13.46	$13.45	$13.50
Purchase #5	$235.60	12.282%	$264.5364	$264.54	$264.55	$264.50
Purchase #6	$176.83	4.394%	$184.5999	$184.60	$184.60	$184.60
Purchase #7	$243.78	10.569%	$269.5451	$269.55	$269.55	$269.50
7 purchase totals =	$931.47		$1,021.8856	$1,021.89	$1,021.90	$1,021.80