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	$141.61	10.607%	$156.6306	$156.63	$156.65	$156.60
Purchase #2	$123.71	8.313%	$133.994	$133.99	$134.00	$134.00
Purchase #3	$110.67	11.865%	$123.801	$123.80	$123.80	$123.80
Purchase #4	$18.41	10.153%	$20.2792	$20.28	$20.30	$20.30
Purchase #5	$210.54	13.490%	$238.9418	$238.94	$238.95	$238.90
Purchase #6	$213.96	13.748%	$243.3752	$243.38	$243.40	$243.40
Purchase #7	$68.31	5.411%	$72.0063	$72.01	$72.00	$72.00
7 purchase totals =	$887.21		$989.0281	$989.03	$989.10	$989.00