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	$202.95	11.390%	$226.066	$226.07	$226.05	$226.10
Purchase #2	$155.77	4.508%	$162.7921	$162.79	$162.80	$162.80
Purchase #3	$84.86	12.682%	$95.6219	$95.62	$95.60	$95.60
Purchase #4	$167.94	11.453%	$187.1742	$187.17	$187.15	$187.20
Purchase #5	$193.86	3.608%	$200.8545	$200.85	$200.85	$200.90
Purchase #6	$189.86	10.150%	$209.1308	$209.13	$209.15	$209.10
Purchase #7	$80.53	11.110%	$89.4769	$89.48	$89.50	$89.50
7 purchase totals =	$1,075.77		$1,171.1164	$1,171.11	$1,171.10	$1,171.20