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	$43.37	5.717%	$45.8495	$45.85	$45.85	$45.80
Purchase #2	$198.38	12.351%	$222.8819	$222.88	$222.90	$222.90
Purchase #3	$56.54	3.643%	$58.5998	$58.60	$58.60	$58.60
Purchase #4	$217.42	7.388%	$233.483	$233.48	$233.50	$233.50
Purchase #5	$195.62	3.863%	$203.1768	$203.18	$203.20	$203.20
Purchase #6	$109.31	12.783%	$123.2831	$123.28	$123.30	$123.30
Purchase #7	$14.42	7.505%	$15.5022	$15.50	$15.50	$15.50
7 purchase totals =	$835.06		$902.7763	$902.77	$902.85	$902.80