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	$204.34	7.412%	$219.4857	$219.49	$219.50	$219.50
Purchase #2	$179.95	11.292%	$200.27	$200.27	$200.25	$200.30
Purchase #3	$167.37	11.733%	$187.0075	$187.01	$187.00	$187.00
Purchase #4	$78.53	8.595%	$85.2797	$85.28	$85.30	$85.30
Purchase #5	$45.85	10.507%	$50.6675	$50.67	$50.65	$50.70
Purchase #6	$41.95	8.752%	$45.6215	$45.62	$45.60	$45.60
Purchase #7	$30.73	10.179%	$33.858	$33.86	$33.85	$33.90
7 purchase totals =	$748.72		$822.1899	$822.20	$822.15	$822.30