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	$127.69	4.409%	$133.3199	$133.32	$133.30	$133.30
Purchase #2	$87.41	10.432%	$96.5286	$96.53	$96.55	$96.50
Purchase #3	$82.57	4.741%	$86.4846	$86.48	$86.50	$86.50
Purchase #4	$204.84	11.439%	$228.2716	$228.27	$228.25	$228.30
Purchase #5	$182.40	13.227%	$206.526	$206.53	$206.55	$206.50
Purchase #6	$64.59	12.369%	$72.5791	$72.58	$72.60	$72.60
Purchase #7	$175.77	8.188%	$190.162	$190.16	$190.15	$190.20
7 purchase totals =	$925.27		$1,013.8718	$1,013.87	$1,013.90	$1,013.90