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	$58.42	5.235%	$61.4783	$61.48	$61.50	$61.50
Purchase #2	$156.93	7.347%	$168.4596	$168.46	$168.45	$168.50
Purchase #3	$126.35	12.515%	$142.1627	$142.16	$142.15	$142.20
Purchase #4	$39.46	7.694%	$42.4961	$42.50	$42.50	$42.50
Purchase #5	$196.96	9.644%	$215.9548	$215.95	$215.95	$216.00
Purchase #6	$93.72	5.694%	$99.0564	$99.06	$99.05	$99.10
Purchase #7	$47.56	7.848%	$51.2925	$51.29	$51.30	$51.30
7 purchase totals =	$719.40		$780.9004	$780.90	$780.90	$781.10