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	$43.61	8.308%	$47.2331	$47.23	$47.25	$47.20
Purchase #2	$111.35	13.673%	$126.5749	$126.57	$126.55	$126.60
Purchase #3	$49.49	12.110%	$55.4832	$55.48	$55.50	$55.50
Purchase #4	$229.67	6.689%	$245.0326	$245.03	$245.05	$245.00
Purchase #5	$41.88	4.276%	$43.6708	$43.67	$43.65	$43.70
Purchase #6	$97.86	13.727%	$111.2932	$111.29	$111.30	$111.30
Purchase #7	$39.90	8.712%	$43.3761	$43.38	$43.40	$43.40
7 purchase totals =	$613.76		$672.6639	$672.65	$672.70	$672.70