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	$94.99	4.608%	$99.3671	$99.37	$99.35	$99.40
Purchase #2	$223.85	6.553%	$238.5189	$238.52	$238.50	$238.50
Purchase #3	$30.64	13.193%	$34.6823	$34.68	$34.70	$34.70
Purchase #4	$119.44	6.556%	$127.2705	$127.27	$127.25	$127.30
Purchase #5	$174.32	4.364%	$181.9273	$181.93	$181.95	$181.90
Purchase #6	$85.34	5.261%	$89.8297	$89.83	$89.85	$89.80
Purchase #7	$232.72	9.430%	$254.6655	$254.67	$254.65	$254.70
7 purchase totals =	$961.30		$1,026.2613	$1,026.27	$1,026.25	$1,026.30