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	$141.44	12.315%	$158.8583	$158.86	$158.85	$158.90
Purchase #2	$177.40	4.442%	$185.2801	$185.28	$185.30	$185.30
Purchase #3	$97.99	12.382%	$110.1231	$110.12	$110.10	$110.10
Purchase #4	$65.92	13.334%	$74.7098	$74.71	$74.70	$74.70
Purchase #5	$229.68	11.845%	$256.8856	$256.89	$256.90	$256.90
Purchase #6	$171.31	10.499%	$189.2958	$189.30	$189.30	$189.30
Purchase #7	$245.80	7.123%	$263.3083	$263.31	$263.30	$263.30
7 purchase totals =	$1,129.54		$1,238.4610	$1,238.47	$1,238.45	$1,238.50