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	$241.57	13.187%	$273.4258	$273.43	$273.45	$273.40
Purchase #2	$178.73	12.342%	$200.7889	$200.79	$200.80	$200.80
Purchase #3	$62.27	7.671%	$67.0467	$67.05	$67.05	$67.00
Purchase #4	$172.80	11.109%	$191.9964	$192.00	$192.00	$192.00
Purchase #5	$143.73	5.362%	$151.4368	$151.44	$151.45	$151.40
Purchase #6	$130.32	13.646%	$148.1035	$148.10	$148.10	$148.10
Purchase #7	$60.71	6.236%	$64.4959	$64.50	$64.50	$64.50
7 purchase totals =	$990.13		$1,097.2940	$1,097.31	$1,097.35	$1,097.20