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	$222.60	8.194%	$240.8398	$240.84	$240.85	$240.80
Purchase #2	$35.97	3.245%	$37.1372	$37.14	$37.15	$37.10
Purchase #3	$168.57	13.768%	$191.7787	$191.78	$191.80	$191.80
Purchase #4	$200.28	12.488%	$225.291	$225.29	$225.30	$225.30
Purchase #5	$66.69	6.631%	$71.1122	$71.11	$71.10	$71.10
Purchase #6	$10.39	11.563%	$11.5914	$11.59	$11.60	$11.60
Purchase #7	$81.39	12.643%	$91.6801	$91.68	$91.70	$91.70
7 purchase totals =	$785.89		$869.4304	$869.43	$869.50	$869.40