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	$129.78	8.103%	$140.2961	$140.30	$140.30	$140.30
Purchase #2	$185.34	6.279%	$196.9775	$196.98	$197.00	$197.00
Purchase #3	$155.78	3.210%	$160.7805	$160.78	$160.80	$160.80
Purchase #4	$234.37	3.751%	$243.1612	$243.16	$243.15	$243.20
Purchase #5	$66.46	5.829%	$70.334	$70.33	$70.35	$70.30
Purchase #6	$162.90	4.107%	$169.5903	$169.59	$169.60	$169.60
Purchase #7	$77.53	11.510%	$86.4537	$86.45	$86.45	$86.50
7 purchase totals =	$1,012.16		$1,067.5933	$1,067.59	$1,067.65	$1,067.70