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	$222.93	3.827%	$231.4615	$231.46	$231.45	$231.50
Purchase #2	$140.37	5.638%	$148.2841	$148.28	$148.30	$148.30
Purchase #3	$35.95	7.404%	$38.6117	$38.61	$38.60	$38.60
Purchase #4	$227.72	10.185%	$250.9133	$250.91	$250.90	$250.90
Purchase #5	$30.77	9.607%	$33.7261	$33.73	$33.75	$33.70
Purchase #6	$195.78	8.382%	$212.1903	$212.19	$212.20	$212.20
Purchase #7	$169.72	9.378%	$185.6363	$185.64	$185.65	$185.60
7 purchase totals =	$1,023.24		$1,100.8233	$1,100.82	$1,100.85	$1,100.80