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	$78.54	6.650%	$83.7629	$83.76	$83.75	$83.80
Purchase #2	$30.72	7.480%	$33.0179	$33.02	$33.00	$33.00
Purchase #3	$109.52	6.632%	$116.7834	$116.78	$116.80	$116.80
Purchase #4	$52.32	3.401%	$54.0994	$54.10	$54.10	$54.10
Purchase #5	$160.87	11.681%	$179.6612	$179.66	$179.65	$179.70
Purchase #6	$227.96	11.135%	$253.3433	$253.34	$253.35	$253.30
Purchase #7	$247.94	6.566%	$264.2197	$264.22	$264.20	$264.20
7 purchase totals =	$907.87		$984.8878	$984.88	$984.85	$984.90