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	$211.57	4.855%	$221.8417	$221.84	$221.85	$221.80
Purchase #2	$219.41	10.604%	$242.6762	$242.68	$242.70	$242.70
Purchase #3	$205.96	13.253%	$233.2559	$233.26	$233.25	$233.30
Purchase #4	$135.46	9.430%	$148.2339	$148.23	$148.25	$148.20
Purchase #5	$82.83	10.570%	$91.5851	$91.59	$91.60	$91.60
Purchase #6	$68.65	5.196%	$72.2171	$72.22	$72.20	$72.20
Purchase #7	$135.77	3.627%	$140.6944	$140.69	$140.70	$140.70
7 purchase totals =	$1,059.65		$1,150.5043	$1,150.51	$1,150.55	$1,150.50