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	$134.63	7.414%	$144.6115	$144.61	$144.60	$144.60
Purchase #2	$89.80	7.105%	$96.1803	$96.18	$96.20	$96.20
Purchase #3	$40.34	12.608%	$45.4261	$45.43	$45.45	$45.40
Purchase #4	$229.40	4.825%	$240.4686	$240.47	$240.45	$240.50
Purchase #5	$92.29	13.593%	$104.835	$104.84	$104.85	$104.80
Purchase #6	$221.86	8.229%	$240.1169	$240.12	$240.10	$240.10
Purchase #7	$176.91	4.215%	$184.3668	$184.37	$184.35	$184.40
7 purchase totals =	$985.23		$1,056.0052	$1,056.02	$1,056.00	$1,056.00