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	$134.66	3.857%	$139.8538	$139.85	$139.85	$139.90
Purchase #2	$245.59	12.563%	$276.4435	$276.44	$276.45	$276.40
Purchase #3	$153.79	13.545%	$174.6209	$174.62	$174.60	$174.60
Purchase #4	$98.62	10.617%	$109.0905	$109.09	$109.10	$109.10
Purchase #5	$95.89	13.841%	$109.1621	$109.16	$109.15	$109.20
Purchase #6	$140.77	9.585%	$154.2628	$154.26	$154.25	$154.30
Purchase #7	$91.48	12.256%	$102.6918	$102.69	$102.70	$102.70
7 purchase totals =	$960.80		$1,066.1254	$1,066.11	$1,066.10	$1,066.20