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	$115.99	5.740%	$122.6478	$122.65	$122.65	$122.60
Purchase #2	$69.71	11.162%	$77.491	$77.49	$77.50	$77.50
Purchase #3	$121.49	12.300%	$136.4333	$136.43	$136.45	$136.40
Purchase #4	$212.86	4.722%	$222.9112	$222.91	$222.90	$222.90
Purchase #5	$81.69	11.404%	$91.0059	$91.01	$91.00	$91.00
Purchase #6	$103.27	12.674%	$116.3584	$116.36	$116.35	$116.40
Purchase #7	$88.28	13.865%	$100.52	$100.52	$100.50	$100.50
7 purchase totals =	$793.29		$867.3676	$867.37	$867.35	$867.30