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	$81.41	5.539%	$85.9193	$85.92	$85.90	$85.90
Purchase #2	$127.32	9.838%	$139.8457	$139.85	$139.85	$139.80
Purchase #3	$213.55	9.476%	$233.786	$233.79	$233.80	$233.80
Purchase #4	$60.58	3.813%	$62.8899	$62.89	$62.90	$62.90
Purchase #5	$141.80	12.501%	$159.5264	$159.53	$159.55	$159.50
Purchase #6	$225.76	12.276%	$253.4743	$253.47	$253.45	$253.50
Purchase #7	$153.97	11.848%	$172.2124	$172.21	$172.20	$172.20
7 purchase totals =	$1,004.39		$1,107.6540	$1,107.66	$1,107.65	$1,107.60