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	$201.97	7.516%	$217.1501	$217.15	$217.15	$217.20
Purchase #2	$35.59	8.148%	$38.4899	$38.49	$38.50	$38.50
Purchase #3	$202.26	3.149%	$208.6292	$208.63	$208.65	$208.60
Purchase #4	$164.62	12.600%	$185.3621	$185.36	$185.35	$185.40
Purchase #5	$163.56	12.522%	$184.041	$184.04	$184.05	$184.00
Purchase #6	$54.97	8.203%	$59.4792	$59.48	$59.50	$59.50
Purchase #7	$89.38	11.262%	$99.446	$99.45	$99.45	$99.40
7 purchase totals =	$912.35		$992.5975	$992.60	$992.65	$992.60