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	$172.60	9.185%	$188.4533	$188.45	$188.45	$188.50
Purchase #2	$65.34	6.485%	$69.5773	$69.58	$69.60	$69.60
Purchase #3	$138.69	11.296%	$154.3564	$154.36	$154.35	$154.40
Purchase #4	$56.95	7.764%	$61.3716	$61.37	$61.35	$61.40
Purchase #5	$250.92	3.484%	$259.6621	$259.66	$259.65	$259.70
Purchase #6	$240.98	7.515%	$259.0896	$259.09	$259.10	$259.10
Purchase #7	$94.41	6.847%	$100.8743	$100.87	$100.85	$100.90
7 purchase totals =	$1,019.89		$1,093.3846	$1,093.38	$1,093.35	$1,093.60