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	$223.32	8.222%	$241.6814	$241.68	$241.70	$241.70
Purchase #2	$85.48	4.570%	$89.3864	$89.39	$89.40	$89.40
Purchase #3	$112.64	10.320%	$124.2644	$124.26	$124.25	$124.30
Purchase #4	$109.40	6.637%	$116.6609	$116.66	$116.65	$116.70
Purchase #5	$182.28	5.311%	$191.9609	$191.96	$191.95	$192.00
Purchase #6	$106.73	4.318%	$111.3386	$111.34	$111.35	$111.30
Purchase #7	$195.77	9.812%	$214.979	$214.98	$215.00	$215.00
7 purchase totals =	$1,015.62		$1,090.2716	$1,090.27	$1,090.30	$1,090.40