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	$118.43	4.585%	$123.86	$123.86	$123.85	$123.90
Purchase #2	$132.84	9.117%	$144.951	$144.95	$144.95	$145.00
Purchase #3	$239.40	6.269%	$254.408	$254.41	$254.40	$254.40
Purchase #4	$111.49	6.428%	$118.6566	$118.66	$118.65	$118.70
Purchase #5	$35.36	9.695%	$38.7882	$38.79	$38.80	$38.80
Purchase #6	$242.57	5.129%	$255.0114	$255.01	$255.00	$255.00
Purchase #7	$206.39	7.530%	$221.9312	$221.93	$221.95	$221.90
7 purchase totals =	$1,086.48		$1,157.6064	$1,157.61	$1,157.60	$1,157.70