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	$61.33	6.701%	$65.4397	$65.44	$65.45	$65.40
Purchase #2	$70.33	11.760%	$78.6008	$78.60	$78.60	$78.60
Purchase #3	$186.93	7.361%	$200.6899	$200.69	$200.70	$200.70
Purchase #4	$248.26	9.128%	$270.9212	$270.92	$270.90	$270.90
Purchase #5	$183.77	12.842%	$207.3697	$207.37	$207.35	$207.40
Purchase #6	$196.54	9.180%	$214.5824	$214.58	$214.60	$214.60
Purchase #7	$118.50	6.799%	$126.5568	$126.56	$126.55	$126.60
7 purchase totals =	$1,065.66		$1,164.1605	$1,164.16	$1,164.15	$1,164.20