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	$148.82	13.515%	$168.933	$168.93	$168.95	$168.90
Purchase #2	$169.87	6.789%	$181.4025	$181.40	$181.40	$181.40
Purchase #3	$26.27	8.111%	$28.4008	$28.40	$28.40	$28.40
Purchase #4	$92.50	3.248%	$95.5044	$95.50	$95.50	$95.50
Purchase #5	$35.94	5.530%	$37.9275	$37.93	$37.95	$37.90
Purchase #6	$76.52	5.343%	$80.6085	$80.61	$80.60	$80.60
Purchase #7	$32.61	3.303%	$33.6871	$33.69	$33.70	$33.70
7 purchase totals =	$582.53		$626.4638	$626.46	$626.50	$626.40