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	$218.57	10.412%	$241.3275	$241.33	$241.35	$241.30
Purchase #2	$148.64	10.856%	$164.7764	$164.78	$164.80	$164.80
Purchase #3	$78.91	13.512%	$89.5723	$89.57	$89.55	$89.60
Purchase #4	$7.91	4.627%	$8.276	$8.28	$8.30	$8.30
Purchase #5	$161.62	10.265%	$178.2103	$178.21	$178.20	$178.20
Purchase #6	$150.84	9.115%	$164.5891	$164.59	$164.60	$164.60
Purchase #7	$241.98	13.651%	$275.0127	$275.01	$275.00	$275.00
7 purchase totals =	$1,008.47		$1,121.7643	$1,121.77	$1,121.80	$1,121.80