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	$138.94	10.732%	$153.851	$153.85	$153.85	$153.90
Purchase #2	$159.79	7.582%	$171.9053	$171.91	$171.90	$171.90
Purchase #3	$138.77	4.114%	$144.479	$144.48	$144.50	$144.50
Purchase #4	$202.81	3.601%	$210.1132	$210.11	$210.10	$210.10
Purchase #5	$247.40	13.667%	$281.2122	$281.21	$281.20	$281.20
Purchase #6	$180.74	8.696%	$196.4572	$196.46	$196.45	$196.50
Purchase #7	$192.75	3.177%	$198.8737	$198.87	$198.85	$198.90
7 purchase totals =	$1,261.20		$1,356.8916	$1,356.89	$1,356.85	$1,357.00