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	$128.83	4.140%	$134.1636	$134.16	$134.15	$134.20
Purchase #2	$28.76	13.352%	$32.6	$32.60	$32.60	$32.60
Purchase #3	$183.51	5.507%	$193.6159	$193.62	$193.60	$193.60
Purchase #4	$196.89	7.622%	$211.897	$211.90	$211.90	$211.90
Purchase #5	$161.52	13.860%	$183.9067	$183.91	$183.90	$183.90
Purchase #6	$91.67	11.664%	$102.3624	$102.36	$102.35	$102.40
Purchase #7	$134.88	4.772%	$141.3165	$141.32	$141.30	$141.30
7 purchase totals =	$926.06		$999.8621	$999.87	$999.80	$999.90