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	$77.80	9.858%	$85.4695	$85.47	$85.45	$85.50
Purchase #2	$77.39	6.293%	$82.2602	$82.26	$82.25	$82.30
Purchase #3	$57.78	11.515%	$64.4334	$64.43	$64.45	$64.40
Purchase #4	$23.91	13.652%	$27.1742	$27.17	$27.15	$27.20
Purchase #5	$48.65	6.736%	$51.9271	$51.93	$51.95	$51.90
Purchase #6	$165.82	7.257%	$177.8536	$177.85	$177.85	$177.90
Purchase #7	$148.70	11.170%	$165.3098	$165.31	$165.30	$165.30
7 purchase totals =	$600.05		$654.4278	$654.42	$654.40	$654.50