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	$88.36	11.263%	$98.312	$98.31	$98.30	$98.30
Purchase #2	$94.83	6.379%	$100.8792	$100.88	$100.90	$100.90
Purchase #3	$65.83	9.303%	$71.9542	$71.95	$71.95	$72.00
Purchase #4	$223.27	4.749%	$233.8731	$233.87	$233.85	$233.90
Purchase #5	$196.68	7.673%	$211.7713	$211.77	$211.75	$211.80
Purchase #6	$205.88	5.829%	$217.8807	$217.88	$217.90	$217.90
Purchase #7	$58.43	10.153%	$64.3624	$64.36	$64.35	$64.40
7 purchase totals =	$933.28		$999.0329	$999.02	$999.00	$999.20