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	$127.99	8.636%	$139.0432	$139.04	$139.05	$139.00
Purchase #2	$190.31	10.145%	$209.6169	$209.62	$209.60	$209.60
Purchase #3	$30.50	10.622%	$33.7397	$33.74	$33.75	$33.70
Purchase #4	$165.87	3.567%	$171.7866	$171.79	$171.80	$171.80
Purchase #5	$83.42	8.359%	$90.3931	$90.39	$90.40	$90.40
Purchase #6	$149.50	12.639%	$168.3953	$168.40	$168.40	$168.40
Purchase #7	$212.99	12.701%	$240.0419	$240.04	$240.05	$240.00
7 purchase totals =	$960.58		$1,053.0167	$1,053.02	$1,053.05	$1,052.90