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	$65.42	11.444%	$72.9067	$72.91	$72.90	$72.90
Purchase #2	$224.89	8.741%	$244.5476	$244.55	$244.55	$244.50
Purchase #3	$174.70	13.654%	$198.5535	$198.55	$198.55	$198.60
Purchase #4	$106.57	5.807%	$112.7585	$112.76	$112.75	$112.80
Purchase #5	$139.30	5.870%	$147.4769	$147.48	$147.50	$147.50
Purchase #6	$93.38	11.862%	$104.4567	$104.46	$104.45	$104.50
Purchase #7	$73.51	12.774%	$82.9002	$82.90	$82.90	$82.90
7 purchase totals =	$877.77		$963.6001	$963.61	$963.60	$963.70