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	$179.89	9.276%	$196.5766	$196.58	$196.60	$196.60
Purchase #2	$86.61	3.175%	$89.3599	$89.36	$89.35	$89.40
Purchase #3	$134.53	7.375%	$144.4516	$144.45	$144.45	$144.50
Purchase #4	$61.78	8.519%	$67.043	$67.04	$67.05	$67.00
Purchase #5	$40.30	11.220%	$44.8217	$44.82	$44.80	$44.80
Purchase #6	$187.80	10.461%	$207.4458	$207.45	$207.45	$207.40
Purchase #7	$184.62	10.815%	$204.5867	$204.59	$204.60	$204.60
7 purchase totals =	$875.53		$954.2853	$954.29	$954.30	$954.30