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	$86.78	3.495%	$89.813	$89.81	$89.80	$89.80
Purchase #2	$128.45	10.784%	$142.302	$142.30	$142.30	$142.30
Purchase #3	$58.45	3.351%	$60.4087	$60.41	$60.40	$60.40
Purchase #4	$148.40	4.103%	$154.4889	$154.49	$154.50	$154.50
Purchase #5	$196.85	8.279%	$213.1472	$213.15	$213.15	$213.10
Purchase #6	$136.86	8.324%	$148.2522	$148.25	$148.25	$148.30
Purchase #7	$228.61	12.440%	$257.0491	$257.05	$257.05	$257.00
7 purchase totals =	$984.40		$1,065.4611	$1,065.46	$1,065.45	$1,065.40