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	$92.41	4.502%	$96.5703	$96.57	$96.55	$96.60
Purchase #2	$227.87	4.490%	$238.1014	$238.10	$238.10	$238.10
Purchase #3	$172.76	4.534%	$180.5929	$180.59	$180.60	$180.60
Purchase #4	$18.88	7.364%	$20.2703	$20.27	$20.25	$20.30
Purchase #5	$52.88	13.242%	$59.8824	$59.88	$59.90	$59.90
Purchase #6	$123.93	6.571%	$132.0734	$132.07	$132.05	$132.10
Purchase #7	$235.46	4.448%	$245.9333	$245.93	$245.95	$245.90
7 purchase totals =	$924.19		$973.4240	$973.41	$973.40	$973.50