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	$229.87	3.539%	$238.0051	$238.01	$238.00	$238.00
Purchase #2	$158.95	13.427%	$180.2922	$180.29	$180.30	$180.30
Purchase #3	$222.28	8.374%	$240.8937	$240.89	$240.90	$240.90
Purchase #4	$35.98	7.322%	$38.6145	$38.61	$38.60	$38.60
Purchase #5	$215.63	9.196%	$235.4593	$235.46	$235.45	$235.50
Purchase #6	$100.33	9.509%	$109.8704	$109.87	$109.85	$109.90
Purchase #7	$106.71	5.588%	$112.673	$112.67	$112.65	$112.70
7 purchase totals =	$1,069.75		$1,155.8082	$1,155.80	$1,155.75	$1,155.90