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	$67.31	3.179%	$69.4498	$69.45	$69.45	$69.40
Purchase #2	$31.40	6.575%	$33.4646	$33.46	$33.45	$33.50
Purchase #3	$50.94	6.827%	$54.4177	$54.42	$54.40	$54.40
Purchase #4	$23.37	4.850%	$24.5034	$24.50	$24.50	$24.50
Purchase #5	$25.85	8.783%	$28.1204	$28.12	$28.10	$28.10
Purchase #6	$201.55	10.787%	$223.2912	$223.29	$223.30	$223.30
Purchase #7	$182.60	9.802%	$200.4985	$200.50	$200.50	$200.50
7 purchase totals =	$583.02		$633.7456	$633.74	$633.70	$633.70