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	$184.72	11.240%	$205.4825	$205.48	$205.50	$205.50
Purchase #2	$89.34	6.201%	$94.88	$94.88	$94.90	$94.90
Purchase #3	$210.76	9.216%	$230.1836	$230.18	$230.20	$230.20
Purchase #4	$12.84	13.255%	$14.5419	$14.54	$14.55	$14.50
Purchase #5	$147.97	7.443%	$158.9834	$158.98	$159.00	$159.00
Purchase #6	$100.53	9.315%	$109.8944	$109.89	$109.90	$109.90
Purchase #7	$243.45	13.722%	$276.8562	$276.86	$276.85	$276.90
7 purchase totals =	$989.61		$1,090.8220	$1,090.81	$1,090.90	$1,090.90