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	$167.82	10.757%	$185.8724	$185.87	$185.85	$185.90
Purchase #2	$228.45	5.212%	$240.3568	$240.36	$240.35	$240.40
Purchase #3	$48.97	12.361%	$55.0232	$55.02	$55.00	$55.00
Purchase #4	$58.98	11.297%	$65.643	$65.64	$65.65	$65.60
Purchase #5	$137.45	7.565%	$147.8481	$147.85	$147.85	$147.80
Purchase #6	$205.80	8.608%	$223.5153	$223.52	$223.50	$223.50
Purchase #7	$192.90	10.565%	$213.2799	$213.28	$213.30	$213.30
7 purchase totals =	$1,040.37		$1,131.5387	$1,131.54	$1,131.50	$1,131.50