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	$41.98	5.108%	$44.1243	$44.12	$44.10	$44.10
Purchase #2	$29.85	12.802%	$33.6714	$33.67	$33.65	$33.70
Purchase #3	$179.34	6.559%	$191.1029	$191.10	$191.10	$191.10
Purchase #4	$99.33	4.540%	$103.8396	$103.84	$103.85	$103.80
Purchase #5	$82.37	12.416%	$92.5971	$92.60	$92.60	$92.60
Purchase #6	$244.50	5.861%	$258.8301	$258.83	$258.85	$258.80
Purchase #7	$41.36	12.423%	$46.4982	$46.50	$46.50	$46.50
7 purchase totals =	$718.73		$770.6636	$770.66	$770.65	$770.60