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	$23.29	4.122%	$24.25	$24.25	$24.25	$24.30
Purchase #2	$229.61	13.623%	$260.8898	$260.89	$260.90	$260.90
Purchase #3	$59.69	3.684%	$61.889	$61.89	$61.90	$61.90
Purchase #4	$35.58	5.625%	$37.5814	$37.58	$37.60	$37.60
Purchase #5	$172.75	4.429%	$180.4011	$180.40	$180.40	$180.40
Purchase #6	$150.34	3.610%	$155.7673	$155.77	$155.75	$155.80
Purchase #7	$245.58	4.461%	$256.5353	$256.54	$256.55	$256.50
7 purchase totals =	$916.84		$977.3139	$977.32	$977.35	$977.40