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	$52.67	9.481%	$57.6636	$57.66	$57.65	$57.70
Purchase #2	$81.58	6.578%	$86.9463	$86.95	$86.95	$86.90
Purchase #3	$170.41	11.238%	$189.5607	$189.56	$189.55	$189.60
Purchase #4	$216.85	12.751%	$244.5005	$244.50	$244.50	$244.50
Purchase #5	$218.76	10.816%	$242.4211	$242.42	$242.40	$242.40
Purchase #6	$30.51	4.514%	$31.8872	$31.89	$31.90	$31.90
Purchase #7	$40.61	4.112%	$42.2799	$42.28	$42.30	$42.30
7 purchase totals =	$811.39		$895.2593	$895.26	$895.25	$895.30