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	$107.58	5.513%	$113.5109	$113.51	$113.50	$113.50
Purchase #2	$232.59	7.758%	$250.6343	$250.63	$250.65	$250.60
Purchase #3	$13.60	13.705%	$15.4639	$15.46	$15.45	$15.50
Purchase #4	$146.81	3.207%	$151.5182	$151.52	$151.50	$151.50
Purchase #5	$167.97	12.703%	$189.3072	$189.31	$189.30	$189.30
Purchase #6	$127.26	7.200%	$136.4227	$136.42	$136.40	$136.40
Purchase #7	$96.28	13.701%	$109.4713	$109.47	$109.45	$109.50
7 purchase totals =	$892.09		$966.3285	$966.32	$966.25	$966.30