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	$237.69	13.441%	$269.6379	$269.64	$269.65	$269.60
Purchase #2	$157.76	7.102%	$168.9641	$168.96	$168.95	$169.00
Purchase #3	$10.68	11.385%	$11.8959	$11.90	$11.90	$11.90
Purchase #4	$172.61	10.526%	$190.7789	$190.78	$190.80	$190.80
Purchase #5	$72.73	11.173%	$80.8561	$80.86	$80.85	$80.90
Purchase #6	$189.51	3.737%	$196.592	$196.59	$196.60	$196.60
Purchase #7	$127.37	8.199%	$137.8131	$137.81	$137.80	$137.80
7 purchase totals =	$968.35		$1,056.5380	$1,056.54	$1,056.55	$1,056.60