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	$155.85	4.851%	$163.4103	$163.41	$163.40	$163.40
Purchase #2	$87.39	10.433%	$96.5074	$96.51	$96.50	$96.50
Purchase #3	$20.69	5.559%	$21.8402	$21.84	$21.85	$21.80
Purchase #4	$165.80	5.612%	$175.1047	$175.10	$175.10	$175.10
Purchase #5	$172.69	9.504%	$189.1025	$189.10	$189.10	$189.10
Purchase #6	$250.60	13.460%	$284.3308	$284.33	$284.35	$284.30
Purchase #7	$176.43	11.437%	$196.6083	$196.61	$196.60	$196.60
7 purchase totals =	$1,029.45		$1,126.9042	$1,126.90	$1,126.90	$1,126.80