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	$117.66	13.269%	$133.2723	$133.27	$133.25	$133.30
Purchase #2	$100.45	8.525%	$109.0134	$109.01	$109.00	$109.00
Purchase #3	$173.50	5.763%	$183.4988	$183.50	$183.50	$183.50
Purchase #4	$188.30	11.315%	$209.6061	$209.61	$209.60	$209.60
Purchase #5	$33.92	5.454%	$35.77	$35.77	$35.75	$35.80
Purchase #6	$119.32	10.163%	$131.4465	$131.45	$131.45	$131.40
Purchase #7	$206.43	4.539%	$215.7999	$215.80	$215.80	$215.80
7 purchase totals =	$939.58		$1,018.4070	$1,018.41	$1,018.35	$1,018.40