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	$236.93	8.427%	$256.8961	$256.90	$256.90	$256.90
Purchase #2	$92.93	6.289%	$98.7744	$98.77	$98.75	$98.80
Purchase #3	$87.35	4.678%	$91.4362	$91.44	$91.45	$91.40
Purchase #4	$98.25	6.102%	$104.2452	$104.25	$104.25	$104.20
Purchase #5	$84.96	13.696%	$96.5961	$96.60	$96.60	$96.60
Purchase #6	$243.61	4.705%	$255.0719	$255.07	$255.05	$255.10
Purchase #7	$101.65	8.713%	$110.5068	$110.51	$110.50	$110.50
7 purchase totals =	$945.68		$1,013.5267	$1,013.54	$1,013.50	$1,013.50