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	$107.69	10.166%	$118.6378	$118.64	$118.65	$118.60
Purchase #2	$48.78	6.152%	$51.7809	$51.78	$51.80	$51.80
Purchase #3	$101.98	4.341%	$106.407	$106.41	$106.40	$106.40
Purchase #4	$87.27	13.459%	$99.0157	$99.02	$99.00	$99.00
Purchase #5	$64.58	12.585%	$72.7074	$72.71	$72.70	$72.70
Purchase #6	$233.83	7.570%	$251.5309	$251.53	$251.55	$251.50
Purchase #7	$116.39	11.342%	$129.591	$129.59	$129.60	$129.60
7 purchase totals =	$760.52		$829.6707	$829.68	$829.70	$829.60