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	$88.46	12.674%	$99.6714	$99.67	$99.65	$99.70
Purchase #2	$7.28	6.600%	$7.7605	$7.76	$7.75	$7.80
Purchase #3	$96.81	3.458%	$100.1577	$100.16	$100.15	$100.20
Purchase #4	$52.94	7.462%	$56.8904	$56.89	$56.90	$56.90
Purchase #5	$65.61	7.182%	$70.3221	$70.32	$70.30	$70.30
Purchase #6	$8.71	6.639%	$9.2883	$9.29	$9.30	$9.30
Purchase #7	$103.31	10.381%	$114.0346	$114.03	$114.05	$114.00
7 purchase totals =	$423.12		$458.1250	$458.12	$458.10	$458.20