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	$129.67	11.719%	$144.866	$144.87	$144.85	$144.90
Purchase #2	$57.26	4.413%	$59.7869	$59.79	$59.80	$59.80
Purchase #3	$212.91	4.105%	$221.65	$221.65	$221.65	$221.70
Purchase #4	$6.56	12.678%	$7.3917	$7.39	$7.40	$7.40
Purchase #5	$246.42	4.102%	$256.5281	$256.53	$256.55	$256.50
Purchase #6	$68.54	10.642%	$75.834	$75.83	$75.85	$75.80
Purchase #7	$196.51	12.223%	$220.5294	$220.53	$220.55	$220.50
7 purchase totals =	$917.87		$986.5861	$986.59	$986.65	$986.60