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	$211.96	8.297%	$229.5463	$229.55	$229.55	$229.50
Purchase #2	$81.91	5.480%	$86.3987	$86.40	$86.40	$86.40
Purchase #3	$124.28	13.142%	$140.6129	$140.61	$140.60	$140.60
Purchase #4	$247.75	13.562%	$281.3499	$281.35	$281.35	$281.30
Purchase #5	$205.93	7.712%	$221.8113	$221.81	$221.80	$221.80
Purchase #6	$50.25	6.683%	$53.6082	$53.61	$53.60	$53.60
Purchase #7	$150.25	12.578%	$169.1484	$169.15	$169.15	$169.10
7 purchase totals =	$1,072.33		$1,182.4757	$1,182.48	$1,182.45	$1,182.30