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	$135.68	4.170%	$141.3379	$141.34	$141.35	$141.30
Purchase #2	$61.70	9.196%	$67.3739	$67.37	$67.35	$67.40
Purchase #3	$10.36	4.153%	$10.7903	$10.79	$10.80	$10.80
Purchase #4	$90.64	10.299%	$99.975	$99.98	$100.00	$100.00
Purchase #5	$36.64	5.613%	$38.6966	$38.70	$38.70	$38.70
Purchase #6	$184.99	3.652%	$191.7458	$191.75	$191.75	$191.70
Purchase #7	$91.80	13.168%	$103.8882	$103.89	$103.90	$103.90
7 purchase totals =	$611.81		$653.8077	$653.82	$653.85	$653.80