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	$210.33	3.856%	$218.4403	$218.44	$218.45	$218.40
Purchase #2	$35.86	4.242%	$37.3812	$37.38	$37.40	$37.40
Purchase #3	$64.92	13.509%	$73.69	$73.69	$73.70	$73.70
Purchase #4	$180.86	12.600%	$203.6484	$203.65	$203.65	$203.60
Purchase #5	$164.32	10.472%	$181.5276	$181.53	$181.55	$181.50
Purchase #6	$33.89	3.399%	$35.0419	$35.04	$35.05	$35.00
Purchase #7	$54.42	11.475%	$60.6647	$60.66	$60.65	$60.70
7 purchase totals =	$744.60		$810.3941	$810.39	$810.45	$810.30