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	$218.94	4.409%	$228.5931	$228.59	$228.60	$228.60
Purchase #2	$13.89	6.386%	$14.777	$14.78	$14.80	$14.80
Purchase #3	$206.92	5.722%	$218.76	$218.76	$218.75	$218.80
Purchase #4	$130.26	5.796%	$137.8099	$137.81	$137.80	$137.80
Purchase #5	$13.70	13.544%	$15.5555	$15.56	$15.55	$15.60
Purchase #6	$85.57	4.668%	$89.5644	$89.56	$89.55	$89.60
Purchase #7	$82.41	7.561%	$88.641	$88.64	$88.65	$88.60
7 purchase totals =	$751.69		$793.7009	$793.70	$793.70	$793.80