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	$245.64	5.272%	$258.5901	$258.59	$258.60	$258.60
Purchase #2	$88.97	4.250%	$92.7512	$92.75	$92.75	$92.80
Purchase #3	$182.80	7.347%	$196.2303	$196.23	$196.25	$196.20
Purchase #4	$86.89	4.138%	$90.4855	$90.49	$90.50	$90.50
Purchase #5	$212.54	11.391%	$236.7504	$236.75	$236.75	$236.80
Purchase #6	$108.78	11.161%	$120.9209	$120.92	$120.90	$120.90
Purchase #7	$125.82	8.730%	$136.8041	$136.80	$136.80	$136.80
7 purchase totals =	$1,051.44		$1,132.5325	$1,132.53	$1,132.55	$1,132.60