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	$210.77	9.367%	$230.5128	$230.51	$230.50	$230.50
Purchase #2	$99.58	13.579%	$113.102	$113.10	$113.10	$113.10
Purchase #3	$187.99	4.680%	$196.7879	$196.79	$196.80	$196.80
Purchase #4	$239.72	3.238%	$247.4821	$247.48	$247.50	$247.50
Purchase #5	$89.76	11.713%	$100.2736	$100.27	$100.25	$100.30
Purchase #6	$80.25	13.278%	$90.9056	$90.91	$90.90	$90.90
Purchase #7	$227.50	12.701%	$256.3948	$256.39	$256.40	$256.40
7 purchase totals =	$1,135.57		$1,235.4588	$1,235.45	$1,235.45	$1,235.50