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	$33.95	9.351%	$37.1247	$37.12	$37.10	$37.10
Purchase #2	$171.94	7.866%	$185.4648	$185.46	$185.45	$185.50
Purchase #3	$101.88	10.368%	$112.4429	$112.44	$112.45	$112.40
Purchase #4	$237.30	13.520%	$269.383	$269.38	$269.40	$269.40
Purchase #5	$229.54	5.547%	$242.2726	$242.27	$242.25	$242.30
Purchase #6	$73.40	8.459%	$79.6089	$79.61	$79.60	$79.60
Purchase #7	$162.37	7.733%	$174.9261	$174.93	$174.95	$174.90
7 purchase totals =	$1,010.38		$1,101.2230	$1,101.21	$1,101.20	$1,101.20