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	$78.46	6.780%	$83.7796	$83.78	$83.80	$83.80
Purchase #2	$99.39	5.786%	$105.1407	$105.14	$105.15	$105.10
Purchase #3	$52.44	13.173%	$59.3479	$59.35	$59.35	$59.30
Purchase #4	$76.67	6.610%	$81.7379	$81.74	$81.75	$81.70
Purchase #5	$81.74	4.548%	$85.4575	$85.46	$85.45	$85.50
Purchase #6	$112.50	6.607%	$119.9329	$119.93	$119.95	$119.90
Purchase #7	$208.27	11.121%	$231.4317	$231.43	$231.45	$231.40
7 purchase totals =	$709.47		$766.8282	$766.83	$766.90	$766.70