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	$233.68	8.658%	$253.912	$253.91	$253.90	$253.90
Purchase #2	$143.36	6.391%	$152.5221	$152.52	$152.50	$152.50
Purchase #3	$55.32	6.859%	$59.1144	$59.11	$59.10	$59.10
Purchase #4	$160.95	4.679%	$168.4809	$168.48	$168.50	$168.50
Purchase #5	$31.60	13.287%	$35.7987	$35.80	$35.80	$35.80
Purchase #6	$169.48	12.592%	$190.8209	$190.82	$190.80	$190.80
Purchase #7	$12.79	6.797%	$13.6593	$13.66	$13.65	$13.70
7 purchase totals =	$807.18		$874.3083	$874.30	$874.25	$874.30