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	$204.41	6.231%	$217.1468	$217.15	$217.15	$217.10
Purchase #2	$85.53	3.328%	$88.3764	$88.38	$88.40	$88.40
Purchase #3	$6.33	12.382%	$7.1138	$7.11	$7.10	$7.10
Purchase #4	$215.90	7.227%	$231.5031	$231.50	$231.50	$231.50
Purchase #5	$167.77	13.787%	$190.9004	$190.90	$190.90	$190.90
Purchase #6	$100.31	5.250%	$105.5763	$105.58	$105.60	$105.60
Purchase #7	$63.89	13.151%	$72.2922	$72.29	$72.30	$72.30
7 purchase totals =	$844.14		$912.9090	$912.91	$912.95	$912.90