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	$233.28	8.390%	$252.8522	$252.85	$252.85	$252.90
Purchase #2	$147.93	6.562%	$157.6372	$157.64	$157.65	$157.60
Purchase #3	$224.46	9.413%	$245.5884	$245.59	$245.60	$245.60
Purchase #4	$213.54	9.364%	$233.5359	$233.54	$233.55	$233.50
Purchase #5	$72.64	5.383%	$76.5502	$76.55	$76.55	$76.60
Purchase #6	$112.41	3.736%	$116.6096	$116.61	$116.60	$116.60
Purchase #7	$84.55	5.625%	$89.3059	$89.31	$89.30	$89.30
7 purchase totals =	$1,088.81		$1,172.0794	$1,172.09	$1,172.10	$1,172.10