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	$150.92	4.681%	$157.9846	$157.98	$158.00	$158.00
Purchase #2	$146.51	8.387%	$158.7978	$158.80	$158.80	$158.80
Purchase #3	$143.39	11.325%	$159.6289	$159.63	$159.65	$159.60
Purchase #4	$210.28	6.276%	$223.4772	$223.48	$223.50	$223.50
Purchase #5	$91.85	5.168%	$96.5968	$96.60	$96.60	$96.60
Purchase #6	$244.50	10.254%	$269.571	$269.57	$269.55	$269.60
Purchase #7	$211.29	10.708%	$233.9149	$233.91	$233.90	$233.90
7 purchase totals =	$1,198.74		$1,299.9712	$1,299.97	$1,300.00	$1,300.00