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	$76.60	4.762%	$80.2477	$80.25	$80.25	$80.20
Purchase #2	$19.58	11.190%	$21.771	$21.77	$21.75	$21.80
Purchase #3	$79.66	13.455%	$90.3783	$90.38	$90.40	$90.40
Purchase #4	$23.32	5.282%	$24.5518	$24.55	$24.55	$24.60
Purchase #5	$12.73	13.585%	$14.4594	$14.46	$14.45	$14.50
Purchase #6	$106.55	3.830%	$110.6309	$110.63	$110.65	$110.60
Purchase #7	$67.27	6.635%	$71.7334	$71.73	$71.75	$71.70
7 purchase totals =	$385.71		$413.7725	$413.77	$413.80	$413.80