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	$231.42	13.706%	$263.1384	$263.14	$263.15	$263.10
Purchase #2	$103.85	8.741%	$112.9275	$112.93	$112.95	$112.90
Purchase #3	$36.88	13.299%	$41.7847	$41.78	$41.80	$41.80
Purchase #4	$209.53	4.740%	$219.4617	$219.46	$219.45	$219.50
Purchase #5	$31.93	5.681%	$33.7439	$33.74	$33.75	$33.70
Purchase #6	$158.59	9.327%	$173.3817	$173.38	$173.40	$173.40
Purchase #7	$53.69	7.852%	$57.9057	$57.91	$57.90	$57.90
7 purchase totals =	$825.89		$902.3436	$902.34	$902.40	$902.30