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	$195.96	12.190%	$219.8475	$219.85	$219.85	$219.80
Purchase #2	$154.27	9.401%	$168.7729	$168.77	$168.75	$168.80
Purchase #3	$200.41	4.707%	$209.8433	$209.84	$209.85	$209.80
Purchase #4	$130.80	12.781%	$147.5175	$147.52	$147.50	$147.50
Purchase #5	$87.46	3.204%	$90.2622	$90.26	$90.25	$90.30
Purchase #6	$34.62	3.487%	$35.8272	$35.83	$35.85	$35.80
Purchase #7	$175.57	3.442%	$181.6131	$181.61	$181.60	$181.60
7 purchase totals =	$979.09		$1,053.6837	$1,053.68	$1,053.65	$1,053.60