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	$221.44	4.718%	$231.8875	$231.89	$231.90	$231.90
Purchase #2	$194.52	11.797%	$217.4675	$217.47	$217.45	$217.50
Purchase #3	$72.76	11.383%	$81.0423	$81.04	$81.05	$81.00
Purchase #4	$113.61	8.698%	$123.4918	$123.49	$123.50	$123.50
Purchase #5	$238.54	7.760%	$257.0507	$257.05	$257.05	$257.10
Purchase #6	$179.82	11.396%	$200.3123	$200.31	$200.30	$200.30
Purchase #7	$179.55	9.874%	$197.2788	$197.28	$197.30	$197.30
7 purchase totals =	$1,200.24		$1,308.5309	$1,308.53	$1,308.55	$1,308.60