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	$79.83	3.376%	$82.5251	$82.53	$82.55	$82.50
Purchase #2	$162.25	6.251%	$172.3922	$172.39	$172.40	$172.40
Purchase #3	$52.48	4.658%	$54.9245	$54.92	$54.90	$54.90
Purchase #4	$244.91	7.788%	$263.9836	$263.98	$264.00	$264.00
Purchase #5	$168.80	4.322%	$176.0955	$176.10	$176.10	$176.10
Purchase #6	$117.83	11.499%	$131.3793	$131.38	$131.40	$131.40
Purchase #7	$133.98	13.724%	$152.3674	$152.37	$152.35	$152.40
7 purchase totals =	$960.08		$1,033.6676	$1,033.67	$1,033.70	$1,033.70