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	$100.55	3.780%	$104.3508	$104.35	$104.35	$104.40
Purchase #2	$208.36	3.696%	$216.061	$216.06	$216.05	$216.10
Purchase #3	$172.31	3.390%	$178.1513	$178.15	$178.15	$178.20
Purchase #4	$200.74	10.720%	$222.2593	$222.26	$222.25	$222.30
Purchase #5	$80.69	3.630%	$83.619	$83.62	$83.60	$83.60
Purchase #6	$211.72	5.843%	$224.0908	$224.09	$224.10	$224.10
Purchase #7	$35.49	7.246%	$38.0616	$38.06	$38.05	$38.10
7 purchase totals =	$1,009.86		$1,066.5938	$1,066.59	$1,066.55	$1,066.80