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	$163.89	4.212%	$170.793	$170.79	$170.80	$170.80
Purchase #2	$172.42	9.646%	$189.0516	$189.05	$189.05	$189.10
Purchase #3	$141.72	4.746%	$148.446	$148.45	$148.45	$148.40
Purchase #4	$92.34	7.338%	$99.1159	$99.12	$99.10	$99.10
Purchase #5	$222.74	5.396%	$234.7591	$234.76	$234.75	$234.80
Purchase #6	$168.31	6.854%	$179.846	$179.85	$179.85	$179.80
Purchase #7	$112.75	12.114%	$126.4085	$126.41	$126.40	$126.40
7 purchase totals =	$1,074.17		$1,148.4201	$1,148.43	$1,148.40	$1,148.40