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	$168.87	7.667%	$181.8173	$181.82	$181.80	$181.80
Purchase #2	$103.87	7.557%	$111.7195	$111.72	$111.70	$111.70
Purchase #3	$96.48	6.246%	$102.5061	$102.51	$102.50	$102.50
Purchase #4	$107.33	12.633%	$120.889	$120.89	$120.90	$120.90
Purchase #5	$58.86	8.853%	$64.0709	$64.07	$64.05	$64.10
Purchase #6	$154.57	5.644%	$163.2939	$163.29	$163.30	$163.30
Purchase #7	$120.94	5.113%	$127.1237	$127.12	$127.10	$127.10
7 purchase totals =	$810.92		$871.4204	$871.42	$871.35	$871.40