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	$207.58	10.456%	$229.2846	$229.28	$229.30	$229.30
Purchase #2	$23.43	8.800%	$25.4918	$25.49	$25.50	$25.50
Purchase #3	$92.89	7.776%	$100.1131	$100.11	$100.10	$100.10
Purchase #4	$133.51	13.144%	$151.0586	$151.06	$151.05	$151.10
Purchase #5	$28.40	10.340%	$31.3366	$31.34	$31.35	$31.30
Purchase #6	$217.78	7.432%	$233.9654	$233.97	$233.95	$234.00
Purchase #7	$86.53	5.323%	$91.136	$91.14	$91.15	$91.10
7 purchase totals =	$790.12		$862.3861	$862.39	$862.40	$862.40