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	$216.85	11.709%	$242.241	$242.24	$242.25	$242.20
Purchase #2	$215.92	5.547%	$227.8971	$227.90	$227.90	$227.90
Purchase #3	$16.73	8.826%	$18.2066	$18.21	$18.20	$18.20
Purchase #4	$75.36	5.543%	$79.5372	$79.54	$79.55	$79.50
Purchase #5	$89.32	12.488%	$100.4743	$100.47	$100.45	$100.50
Purchase #6	$144.88	12.134%	$162.4597	$162.46	$162.45	$162.50
Purchase #7	$25.37	8.456%	$27.5153	$27.52	$27.50	$27.50
7 purchase totals =	$784.43		$858.3312	$858.34	$858.30	$858.30