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	$62.49	13.446%	$70.8924	$70.89	$70.90	$70.90
Purchase #2	$80.73	6.345%	$85.8523	$85.85	$85.85	$85.90
Purchase #3	$152.37	5.739%	$161.1145	$161.11	$161.10	$161.10
Purchase #4	$201.66	8.849%	$219.5049	$219.50	$219.50	$219.50
Purchase #5	$114.69	13.736%	$130.4438	$130.44	$130.45	$130.40
Purchase #6	$143.27	6.126%	$152.0467	$152.05	$152.05	$152.00
Purchase #7	$98.38	5.504%	$103.7948	$103.79	$103.80	$103.80
7 purchase totals =	$853.59		$923.6494	$923.63	$923.65	$923.60