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	$67.89	7.323%	$72.8616	$72.86	$72.85	$72.90
Purchase #2	$165.58	11.730%	$185.0025	$185.00	$185.00	$185.00
Purchase #3	$52.58	6.333%	$55.9099	$55.91	$55.90	$55.90
Purchase #4	$90.79	12.133%	$101.8056	$101.81	$101.80	$101.80
Purchase #5	$171.69	6.693%	$183.1812	$183.18	$183.20	$183.20
Purchase #6	$72.95	11.697%	$81.483	$81.48	$81.50	$81.50
Purchase #7	$158.88	9.733%	$174.3438	$174.34	$174.35	$174.30
7 purchase totals =	$780.36		$854.5876	$854.58	$854.60	$854.60