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	$142.57	4.175%	$148.5223	$148.52	$148.50	$148.50
Purchase #2	$96.71	4.111%	$100.6857	$100.69	$100.70	$100.70
Purchase #3	$127.51	3.532%	$132.0137	$132.01	$132.00	$132.00
Purchase #4	$229.36	5.655%	$242.3303	$242.33	$242.35	$242.30
Purchase #5	$206.67	9.638%	$226.5889	$226.59	$226.60	$226.60
Purchase #6	$167.76	4.259%	$174.9049	$174.90	$174.90	$174.90
Purchase #7	$243.46	7.709%	$262.2283	$262.23	$262.25	$262.20
7 purchase totals =	$1,214.04		$1,287.2741	$1,287.27	$1,287.30	$1,287.20