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	$58.35	4.206%	$60.8042	$60.80	$60.80	$60.80
Purchase #2	$191.77	10.211%	$211.3516	$211.35	$211.35	$211.40
Purchase #3	$37.90	10.518%	$41.8863	$41.89	$41.90	$41.90
Purchase #4	$87.37	8.355%	$94.6698	$94.67	$94.65	$94.70
Purchase #5	$167.83	12.504%	$188.8155	$188.82	$188.80	$188.80
Purchase #6	$99.28	9.351%	$108.5637	$108.56	$108.55	$108.60
Purchase #7	$198.83	11.826%	$222.3436	$222.34	$222.35	$222.30
7 purchase totals =	$841.33		$928.4347	$928.43	$928.40	$928.50