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	$134.85	11.867%	$150.8526	$150.85	$150.85	$150.90
Purchase #2	$146.95	5.637%	$155.2336	$155.23	$155.25	$155.20
Purchase #3	$42.95	9.610%	$47.0775	$47.08	$47.10	$47.10
Purchase #4	$112.34	11.653%	$125.431	$125.43	$125.45	$125.40
Purchase #5	$163.74	13.551%	$185.9284	$185.93	$185.95	$185.90
Purchase #6	$160.37	7.226%	$171.9583	$171.96	$171.95	$172.00
Purchase #7	$159.39	13.601%	$181.0686	$181.07	$181.05	$181.10
7 purchase totals =	$920.59		$1,017.5500	$1,017.55	$1,017.60	$1,017.60