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	$54.89	13.521%	$62.3117	$62.31	$62.30	$62.30
Purchase #2	$205.78	10.421%	$227.2243	$227.22	$227.20	$227.20
Purchase #3	$229.57	7.606%	$247.0311	$247.03	$247.05	$247.00
Purchase #4	$212.32	5.296%	$223.5645	$223.56	$223.55	$223.60
Purchase #5	$217.52	7.800%	$234.4866	$234.49	$234.50	$234.50
Purchase #6	$69.41	12.577%	$78.1397	$78.14	$78.15	$78.10
Purchase #7	$146.30	5.789%	$154.7693	$154.77	$154.75	$154.80
7 purchase totals =	$1,135.79		$1,227.5272	$1,227.52	$1,227.50	$1,227.50