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	$162.73	13.634%	$184.9166	$184.92	$184.90	$184.90
Purchase #2	$37.80	12.680%	$42.593	$42.59	$42.60	$42.60
Purchase #3	$89.63	3.570%	$92.8298	$92.83	$92.85	$92.80
Purchase #4	$143.37	9.439%	$156.9027	$156.90	$156.90	$156.90
Purchase #5	$160.29	13.207%	$181.4595	$181.46	$181.45	$181.50
Purchase #6	$20.39	10.228%	$22.4755	$22.48	$22.50	$22.50
Purchase #7	$89.28	13.641%	$101.4587	$101.46	$101.45	$101.50
7 purchase totals =	$703.49		$782.6358	$782.64	$782.65	$782.70