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	$85.66	5.329%	$90.2248	$90.22	$90.20	$90.20
Purchase #2	$27.39	11.363%	$30.5023	$30.50	$30.50	$30.50
Purchase #3	$40.37	12.452%	$45.3969	$45.40	$45.40	$45.40
Purchase #4	$173.72	3.427%	$179.6734	$179.67	$179.65	$179.70
Purchase #5	$90.45	6.712%	$96.521	$96.52	$96.50	$96.50
Purchase #6	$224.91	11.168%	$250.0279	$250.03	$250.05	$250.00
Purchase #7	$192.56	12.405%	$216.4471	$216.45	$216.45	$216.40
7 purchase totals =	$835.06		$908.7934	$908.79	$908.75	$908.70