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	$95.49	7.402%	$102.5582	$102.56	$102.55	$102.60
Purchase #2	$44.66	7.323%	$47.9305	$47.93	$47.95	$47.90
Purchase #3	$70.38	4.392%	$73.4711	$73.47	$73.45	$73.50
Purchase #4	$131.48	11.598%	$146.7291	$146.73	$146.75	$146.70
Purchase #5	$179.83	5.808%	$190.2745	$190.27	$190.25	$190.30
Purchase #6	$33.63	11.612%	$37.5351	$37.54	$37.55	$37.50
Purchase #7	$185.74	12.765%	$209.4497	$209.45	$209.45	$209.40
7 purchase totals =	$741.21		$807.9482	$807.95	$807.95	$807.90