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	$223.69	4.315%	$233.3422	$233.34	$233.35	$233.30
Purchase #2	$94.52	7.733%	$101.8292	$101.83	$101.85	$101.80
Purchase #3	$115.48	9.285%	$126.2023	$126.20	$126.20	$126.20
Purchase #4	$172.82	5.497%	$182.3199	$182.32	$182.30	$182.30
Purchase #5	$125.59	13.317%	$142.3148	$142.31	$142.30	$142.30
Purchase #6	$244.90	6.125%	$259.9001	$259.90	$259.90	$259.90
Purchase #7	$79.89	7.367%	$85.7755	$85.78	$85.80	$85.80
7 purchase totals =	$1,056.89		$1,131.6840	$1,131.68	$1,131.70	$1,131.60