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	$164.71	5.575%	$173.8926	$173.89	$173.90	$173.90
Purchase #2	$87.28	13.332%	$98.9162	$98.92	$98.90	$98.90
Purchase #3	$44.80	12.737%	$50.5062	$50.51	$50.50	$50.50
Purchase #4	$73.62	12.348%	$82.7106	$82.71	$82.70	$82.70
Purchase #5	$184.78	12.286%	$207.4821	$207.48	$207.50	$207.50
Purchase #6	$101.75	9.579%	$111.4966	$111.50	$111.50	$111.50
Purchase #7	$148.62	13.200%	$168.2378	$168.24	$168.25	$168.20
7 purchase totals =	$805.56		$893.2421	$893.25	$893.25	$893.20