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	$241.48	9.338%	$264.0294	$264.03	$264.05	$264.00
Purchase #2	$123.84	3.726%	$128.4543	$128.45	$128.45	$128.50
Purchase #3	$53.26	3.590%	$55.172	$55.17	$55.15	$55.20
Purchase #4	$235.45	6.221%	$250.0973	$250.10	$250.10	$250.10
Purchase #5	$62.25	13.795%	$70.8374	$70.84	$70.85	$70.80
Purchase #6	$131.29	8.832%	$142.8855	$142.89	$142.90	$142.90
Purchase #7	$127.75	10.150%	$140.7166	$140.72	$140.70	$140.70
7 purchase totals =	$975.32		$1,052.1925	$1,052.20	$1,052.20	$1,052.20