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	$112.51	10.103%	$123.8769	$123.88	$123.90	$123.90
Purchase #2	$101.84	7.285%	$109.259	$109.26	$109.25	$109.30
Purchase #3	$115.46	11.577%	$128.8268	$128.83	$128.85	$128.80
Purchase #4	$179.78	7.845%	$193.8837	$193.88	$193.90	$193.90
Purchase #5	$225.31	11.596%	$251.4369	$251.44	$251.45	$251.40
Purchase #6	$37.87	12.372%	$42.5553	$42.56	$42.55	$42.60
Purchase #7	$216.81	8.731%	$235.7397	$235.74	$235.75	$235.70
7 purchase totals =	$989.58		$1,085.5783	$1,085.59	$1,085.65	$1,085.60