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	$32.37	4.499%	$33.8263	$33.83	$33.85	$33.80
Purchase #2	$121.67	8.152%	$131.5885	$131.59	$131.60	$131.60
Purchase #3	$137.47	3.108%	$141.7426	$141.74	$141.75	$141.70
Purchase #4	$85.79	8.781%	$93.3232	$93.32	$93.30	$93.30
Purchase #5	$236.73	5.454%	$249.6413	$249.64	$249.65	$249.60
Purchase #6	$95.62	12.239%	$107.3229	$107.32	$107.30	$107.30
Purchase #7	$85.82	5.833%	$90.8259	$90.83	$90.85	$90.80
7 purchase totals =	$795.47		$848.2707	$848.27	$848.30	$848.10