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	$96.80	4.733%	$101.3815	$101.38	$101.40	$101.40
Purchase #2	$135.44	3.639%	$140.3687	$140.37	$140.35	$140.40
Purchase #3	$89.67	10.694%	$99.2593	$99.26	$99.25	$99.30
Purchase #4	$82.30	13.686%	$93.5636	$93.56	$93.55	$93.60
Purchase #5	$221.83	9.508%	$242.9216	$242.92	$242.90	$242.90
Purchase #6	$158.92	6.279%	$168.8986	$168.90	$168.90	$168.90
Purchase #7	$214.50	4.290%	$223.7021	$223.70	$223.70	$223.70
7 purchase totals =	$999.46		$1,070.0954	$1,070.09	$1,070.05	$1,070.20