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	$33.34	11.768%	$37.2635	$37.26	$37.25	$37.30
Purchase #2	$57.82	5.649%	$61.0863	$61.09	$61.10	$61.10
Purchase #3	$143.44	10.725%	$158.8239	$158.82	$158.80	$158.80
Purchase #4	$185.33	11.126%	$205.9498	$205.95	$205.95	$205.90
Purchase #5	$96.90	8.686%	$105.3167	$105.32	$105.30	$105.30
Purchase #6	$177.84	10.210%	$195.9975	$196.00	$196.00	$196.00
Purchase #7	$239.97	12.687%	$270.415	$270.42	$270.40	$270.40
7 purchase totals =	$934.64		$1,034.8527	$1,034.86	$1,034.80	$1,034.80