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	$11.58	5.257%	$12.1888	$12.19	$12.20	$12.20
Purchase #2	$121.44	5.109%	$127.6444	$127.64	$127.65	$127.60
Purchase #3	$59.45	6.781%	$63.4813	$63.48	$63.50	$63.50
Purchase #4	$219.33	11.644%	$244.8688	$244.87	$244.85	$244.90
Purchase #5	$189.60	5.870%	$200.7295	$200.73	$200.75	$200.70
Purchase #6	$34.65	12.868%	$39.1088	$39.11	$39.10	$39.10
Purchase #7	$37.88	6.467%	$40.3297	$40.33	$40.35	$40.30
7 purchase totals =	$673.93		$728.3513	$728.35	$728.40	$728.30