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	$122.73	6.464%	$130.6633	$130.66	$130.65	$130.70
Purchase #2	$100.75	8.334%	$109.1465	$109.15	$109.15	$109.10
Purchase #3	$29.35	8.625%	$31.8814	$31.88	$31.90	$31.90
Purchase #4	$159.52	7.783%	$171.9354	$171.94	$171.95	$171.90
Purchase #5	$48.72	9.867%	$53.5272	$53.53	$53.55	$53.50
Purchase #6	$93.28	6.565%	$99.4038	$99.40	$99.40	$99.40
Purchase #7	$129.87	8.558%	$140.9843	$140.98	$141.00	$141.00
7 purchase totals =	$684.22		$737.5419	$737.54	$737.60	$737.50