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	$192.76	7.338%	$206.9047	$206.90	$206.90	$206.90
Purchase #2	$148.58	11.444%	$165.5835	$165.58	$165.60	$165.60
Purchase #3	$198.76	5.388%	$209.4692	$209.47	$209.45	$209.50
Purchase #4	$150.46	5.498%	$158.7323	$158.73	$158.75	$158.70
Purchase #5	$38.30	9.735%	$42.0285	$42.03	$42.05	$42.00
Purchase #6	$147.55	4.284%	$153.871	$153.87	$153.85	$153.90
Purchase #7	$55.38	7.379%	$59.4665	$59.47	$59.45	$59.50
7 purchase totals =	$931.79		$996.0557	$996.05	$996.05	$996.10