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	$113.94	13.630%	$129.47	$129.47	$129.45	$129.50
Purchase #2	$169.38	6.189%	$179.8629	$179.86	$179.85	$179.90
Purchase #3	$15.65	4.864%	$16.4112	$16.41	$16.40	$16.40
Purchase #4	$237.50	11.215%	$264.1356	$264.14	$264.15	$264.10
Purchase #5	$167.93	13.357%	$190.3604	$190.36	$190.35	$190.40
Purchase #6	$230.76	8.654%	$250.73	$250.73	$250.75	$250.70
Purchase #7	$160.81	5.444%	$169.5645	$169.56	$169.55	$169.60
7 purchase totals =	$1,095.97		$1,200.5346	$1,200.53	$1,200.50	$1,200.60