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	$95.44	12.564%	$107.4311	$107.43	$107.45	$107.40
Purchase #2	$232.48	5.161%	$244.4783	$244.48	$244.50	$244.50
Purchase #3	$184.80	8.568%	$200.6337	$200.63	$200.65	$200.60
Purchase #4	$69.90	12.127%	$78.3768	$78.38	$78.40	$78.40
Purchase #5	$33.79	5.683%	$35.7103	$35.71	$35.70	$35.70
Purchase #6	$187.72	6.865%	$200.607	$200.61	$200.60	$200.60
Purchase #7	$204.50	3.677%	$212.0195	$212.02	$212.00	$212.00
7 purchase totals =	$1,008.63		$1,079.2567	$1,079.26	$1,079.30	$1,079.20