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	$183.30	6.768%	$195.7057	$195.71	$195.70	$195.70
Purchase #2	$163.39	10.111%	$179.9104	$179.91	$179.90	$179.90
Purchase #3	$160.43	5.723%	$169.6114	$169.61	$169.60	$169.60
Purchase #4	$213.48	11.435%	$237.8914	$237.89	$237.90	$237.90
Purchase #5	$53.90	5.250%	$56.7298	$56.73	$56.75	$56.70
Purchase #6	$131.53	7.782%	$141.7657	$141.77	$141.75	$141.80
Purchase #7	$30.51	4.592%	$31.911	$31.91	$31.90	$31.90
7 purchase totals =	$936.54		$1,013.5254	$1,013.53	$1,013.50	$1,013.50