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	$195.57	12.861%	$220.7223	$220.72	$220.70	$220.70
Purchase #2	$49.60	12.227%	$55.6646	$55.66	$55.65	$55.70
Purchase #3	$168.33	6.206%	$178.7766	$178.78	$178.80	$178.80
Purchase #4	$93.70	7.220%	$100.4651	$100.47	$100.45	$100.50
Purchase #5	$242.58	11.547%	$270.5907	$270.59	$270.60	$270.60
Purchase #6	$188.89	5.823%	$199.8891	$199.89	$199.90	$199.90
Purchase #7	$247.79	10.696%	$274.2936	$274.29	$274.30	$274.30
7 purchase totals =	$1,186.46		$1,300.4020	$1,300.40	$1,300.40	$1,300.50