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	$77.59	11.773%	$86.7247	$86.72	$86.70	$86.70
Purchase #2	$132.96	10.638%	$147.1043	$147.10	$147.10	$147.10
Purchase #3	$197.81	12.455%	$222.4472	$222.45	$222.45	$222.40
Purchase #4	$5.97	11.647%	$6.6653	$6.67	$6.65	$6.70
Purchase #5	$29.61	10.127%	$32.6086	$32.61	$32.60	$32.60
Purchase #6	$7.32	6.369%	$7.7862	$7.79	$7.80	$7.80
Purchase #7	$78.91	11.835%	$88.249	$88.25	$88.25	$88.20
7 purchase totals =	$530.17		$591.5853	$591.59	$591.55	$591.50