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	$157.73	4.249%	$164.4319	$164.43	$164.45	$164.40
Purchase #2	$73.38	7.529%	$78.9048	$78.90	$78.90	$78.90
Purchase #3	$6.75	7.326%	$7.2445	$7.24	$7.25	$7.20
Purchase #4	$168.62	10.313%	$186.0098	$186.01	$186.00	$186.00
Purchase #5	$183.38	4.226%	$191.1296	$191.13	$191.15	$191.10
Purchase #6	$99.51	13.471%	$112.915	$112.92	$112.90	$112.90
Purchase #7	$203.35	13.329%	$230.4545	$230.45	$230.45	$230.50
7 purchase totals =	$892.72		$971.0901	$971.08	$971.10	$971.00