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	$235.30	13.735%	$267.6185	$267.62	$267.60	$267.60
Purchase #2	$34.63	3.554%	$35.8608	$35.86	$35.85	$35.90
Purchase #3	$32.50	10.492%	$35.9099	$35.91	$35.90	$35.90
Purchase #4	$154.98	7.180%	$166.1076	$166.11	$166.10	$166.10
Purchase #5	$55.32	7.692%	$59.5752	$59.58	$59.60	$59.60
Purchase #6	$240.34	13.424%	$272.6032	$272.60	$272.60	$272.60
Purchase #7	$102.37	8.851%	$111.4308	$111.43	$111.45	$111.40
7 purchase totals =	$855.44		$949.1060	$949.11	$949.10	$949.10