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	$91.48	8.773%	$99.5055	$99.51	$99.50	$99.50
Purchase #2	$164.89	10.716%	$182.5596	$182.56	$182.55	$182.60
Purchase #3	$188.93	12.518%	$212.5803	$212.58	$212.60	$212.60
Purchase #4	$83.51	6.789%	$89.1795	$89.18	$89.20	$89.20
Purchase #5	$139.59	9.754%	$153.2056	$153.21	$153.20	$153.20
Purchase #6	$148.92	5.499%	$157.1091	$157.11	$157.10	$157.10
Purchase #7	$181.56	5.483%	$191.5149	$191.51	$191.50	$191.50
7 purchase totals =	$998.88		$1,085.6545	$1,085.66	$1,085.65	$1,085.70