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	$161.42	6.643%	$172.1431	$172.14	$172.15	$172.10
Purchase #2	$216.54	11.233%	$240.8639	$240.86	$240.85	$240.90
Purchase #3	$94.53	3.723%	$98.0494	$98.05	$98.05	$98.00
Purchase #4	$78.48	6.243%	$83.3795	$83.38	$83.40	$83.40
Purchase #5	$239.79	3.764%	$248.8157	$248.82	$248.80	$248.80
Purchase #6	$172.41	10.147%	$189.9044	$189.90	$189.90	$189.90
Purchase #7	$144.73	8.709%	$157.3345	$157.33	$157.35	$157.30
7 purchase totals =	$1,107.90		$1,190.4905	$1,190.48	$1,190.50	$1,190.40