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	$37.28	11.557%	$41.5884	$41.59	$41.60	$41.60
Purchase #2	$152.84	9.485%	$167.3369	$167.34	$167.35	$167.30
Purchase #3	$176.95	4.698%	$185.2631	$185.26	$185.25	$185.30
Purchase #4	$209.53	8.628%	$227.6082	$227.61	$227.60	$227.60
Purchase #5	$36.40	13.299%	$41.2408	$41.24	$41.25	$41.20
Purchase #6	$218.57	7.299%	$234.5234	$234.52	$234.50	$234.50
Purchase #7	$154.89	10.871%	$171.7281	$171.73	$171.75	$171.70
7 purchase totals =	$986.46		$1,069.2889	$1,069.29	$1,069.30	$1,069.20