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	$149.98	3.425%	$155.1168	$155.12	$155.10	$155.10
Purchase #2	$146.32	12.648%	$164.8266	$164.83	$164.85	$164.80
Purchase #3	$95.27	10.189%	$104.9771	$104.98	$105.00	$105.00
Purchase #4	$177.59	7.516%	$190.9377	$190.94	$190.95	$190.90
Purchase #5	$92.69	5.187%	$97.4978	$97.50	$97.50	$97.50
Purchase #6	$81.99	9.185%	$89.5208	$89.52	$89.50	$89.50
Purchase #7	$153.81	5.487%	$162.2496	$162.25	$162.25	$162.20
7 purchase totals =	$897.65		$965.1264	$965.14	$965.15	$965.00