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	$103.34	8.492%	$112.1156	$112.12	$112.10	$112.10
Purchase #2	$35.34	7.781%	$38.0898	$38.09	$38.10	$38.10
Purchase #3	$134.86	11.852%	$150.8436	$150.84	$150.85	$150.80
Purchase #4	$127.85	6.669%	$136.3763	$136.38	$136.40	$136.40
Purchase #5	$147.91	9.545%	$162.028	$162.03	$162.05	$162.00
Purchase #6	$153.60	11.518%	$171.2916	$171.29	$171.30	$171.30
Purchase #7	$92.47	13.405%	$104.8656	$104.87	$104.85	$104.90
7 purchase totals =	$795.37		$875.6105	$875.62	$875.65	$875.60