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	$33.90	10.109%	$37.327	$37.33	$37.35	$37.30
Purchase #2	$168.47	10.306%	$185.8325	$185.83	$185.85	$185.80
Purchase #3	$160.29	7.275%	$171.9511	$171.95	$171.95	$172.00
Purchase #4	$139.30	8.866%	$151.6503	$151.65	$151.65	$151.70
Purchase #5	$125.44	7.716%	$135.119	$135.12	$135.10	$135.10
Purchase #6	$127.27	8.318%	$137.8563	$137.86	$137.85	$137.90
Purchase #7	$184.62	11.517%	$205.8827	$205.88	$205.90	$205.90
7 purchase totals =	$939.29		$1,025.6189	$1,025.62	$1,025.65	$1,025.70