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	$41.36	6.227%	$43.9355	$43.94	$43.95	$43.90
Purchase #2	$38.94	6.218%	$41.3613	$41.36	$41.35	$41.40
Purchase #3	$47.45	12.854%	$53.5492	$53.55	$53.55	$53.50
Purchase #4	$119.78	10.495%	$132.3509	$132.35	$132.35	$132.40
Purchase #5	$66.28	4.385%	$69.1864	$69.19	$69.20	$69.20
Purchase #6	$37.87	10.427%	$41.8187	$41.82	$41.80	$41.80
Purchase #7	$123.70	6.489%	$131.7269	$131.73	$131.75	$131.70
7 purchase totals =	$475.38		$513.9289	$513.94	$513.95	$513.90