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	$99.90	7.836%	$107.7282	$107.73	$107.75	$107.70
Purchase #2	$42.65	7.585%	$45.885	$45.89	$45.90	$45.90
Purchase #3	$94.58	6.637%	$100.8573	$100.86	$100.85	$100.90
Purchase #4	$208.53	7.498%	$224.1656	$224.17	$224.15	$224.20
Purchase #5	$201.35	3.866%	$209.1342	$209.13	$209.15	$209.10
Purchase #6	$148.42	9.554%	$162.6	$162.60	$162.60	$162.60
Purchase #7	$233.77	9.590%	$256.1885	$256.19	$256.20	$256.20
7 purchase totals =	$1,029.20		$1,106.5588	$1,106.57	$1,106.60	$1,106.60