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	$31.98	11.198%	$35.5611	$35.56	$35.55	$35.60
Purchase #2	$202.90	9.813%	$222.8106	$222.81	$222.80	$222.80
Purchase #3	$41.94	10.644%	$46.4041	$46.40	$46.40	$46.40
Purchase #4	$123.49	6.597%	$131.6366	$131.64	$131.65	$131.60
Purchase #5	$241.73	5.574%	$255.204	$255.20	$255.20	$255.20
Purchase #6	$171.72	13.858%	$195.517	$195.52	$195.50	$195.50
Purchase #7	$136.48	4.832%	$143.0747	$143.07	$143.05	$143.10
7 purchase totals =	$950.24		$1,030.2081	$1,030.20	$1,030.15	$1,030.20