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	$149.79	10.782%	$165.9404	$165.94	$165.95	$165.90
Purchase #2	$242.82	8.235%	$262.8162	$262.82	$262.80	$262.80
Purchase #3	$185.33	6.569%	$197.5043	$197.50	$197.50	$197.50
Purchase #4	$21.69	10.541%	$23.9763	$23.98	$24.00	$24.00
Purchase #5	$168.26	8.167%	$182.0018	$182.00	$182.00	$182.00
Purchase #6	$225.43	13.454%	$255.7594	$255.76	$255.75	$255.80
Purchase #7	$153.28	9.543%	$167.9075	$167.91	$167.90	$167.90
7 purchase totals =	$1,146.60		$1,255.9059	$1,255.91	$1,255.90	$1,255.90