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	$54.64	10.796%	$60.5389	$60.54	$60.55	$60.50
Purchase #2	$201.38	4.192%	$209.8218	$209.82	$209.80	$209.80
Purchase #3	$74.33	5.824%	$78.659	$78.66	$78.65	$78.70
Purchase #4	$114.96	7.443%	$123.5165	$123.52	$123.50	$123.50
Purchase #5	$26.31	9.650%	$28.8489	$28.85	$28.85	$28.80
Purchase #6	$237.64	7.272%	$254.9212	$254.92	$254.90	$254.90
Purchase #7	$26.36	13.213%	$29.8429	$29.84	$29.85	$29.80
7 purchase totals =	$735.62		$786.1492	$786.15	$786.10	$786.00