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	$245.76	13.171%	$278.129	$278.13	$278.15	$278.10
Purchase #2	$95.83	3.788%	$99.46	$99.46	$99.45	$99.50
Purchase #3	$136.78	3.600%	$141.7041	$141.70	$141.70	$141.70
Purchase #4	$167.48	6.790%	$178.8519	$178.85	$178.85	$178.90
Purchase #5	$16.62	11.340%	$18.5047	$18.50	$18.50	$18.50
Purchase #6	$92.90	11.177%	$103.2834	$103.28	$103.30	$103.30
Purchase #7	$227.27	9.331%	$248.4766	$248.48	$248.50	$248.50
7 purchase totals =	$982.64		$1,068.4097	$1,068.40	$1,068.45	$1,068.50