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	$86.51	13.812%	$98.4588	$98.46	$98.45	$98.50
Purchase #2	$61.63	13.225%	$69.7806	$69.78	$69.80	$69.80
Purchase #3	$242.75	11.821%	$271.4455	$271.45	$271.45	$271.40
Purchase #4	$18.46	12.517%	$20.7706	$20.77	$20.75	$20.80
Purchase #5	$232.71	5.288%	$245.0157	$245.02	$245.00	$245.00
Purchase #6	$138.43	4.441%	$144.5777	$144.58	$144.60	$144.60
Purchase #7	$154.37	3.720%	$160.1126	$160.11	$160.10	$160.10
7 purchase totals =	$934.86		$1,010.1615	$1,010.17	$1,010.15	$1,010.20