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	$168.88	4.796%	$176.9795	$176.98	$177.00	$177.00
Purchase #2	$5.69	12.219%	$6.3853	$6.39	$6.40	$6.40
Purchase #3	$247.98	6.624%	$264.4062	$264.41	$264.40	$264.40
Purchase #4	$111.74	10.195%	$123.1319	$123.13	$123.15	$123.10
Purchase #5	$119.76	10.730%	$132.6102	$132.61	$132.60	$132.60
Purchase #6	$190.70	10.357%	$210.4508	$210.45	$210.45	$210.50
Purchase #7	$131.61	4.764%	$137.8799	$137.88	$137.90	$137.90
7 purchase totals =	$976.36		$1,051.8438	$1,051.85	$1,051.90	$1,051.90