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	$50.89	11.288%	$56.6345	$56.63	$56.65	$56.60
Purchase #2	$216.46	10.271%	$238.6926	$238.69	$238.70	$238.70
Purchase #3	$92.56	7.693%	$99.6806	$99.68	$99.70	$99.70
Purchase #4	$128.94	9.325%	$140.9637	$140.96	$140.95	$141.00
Purchase #5	$231.42	5.173%	$243.3914	$243.39	$243.40	$243.40
Purchase #6	$147.60	11.618%	$164.7482	$164.75	$164.75	$164.70
Purchase #7	$224.62	11.515%	$250.485	$250.49	$250.50	$250.50
7 purchase totals =	$1,092.49		$1,194.5960	$1,194.59	$1,194.65	$1,194.60