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	$151.62	6.484%	$161.451	$161.45	$161.45	$161.50
Purchase #2	$156.52	9.543%	$171.4567	$171.46	$171.45	$171.50
Purchase #3	$31.80	7.847%	$34.2953	$34.30	$34.30	$34.30
Purchase #4	$246.41	6.588%	$262.6435	$262.64	$262.65	$262.60
Purchase #5	$150.90	11.661%	$168.4964	$168.50	$168.50	$168.50
Purchase #6	$45.73	9.587%	$50.1141	$50.11	$50.10	$50.10
Purchase #7	$38.30	11.697%	$42.78	$42.78	$42.80	$42.80
7 purchase totals =	$821.28		$891.2370	$891.24	$891.25	$891.30