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	$245.53	6.863%	$262.3807	$262.38	$262.40	$262.40
Purchase #2	$131.43	10.315%	$144.987	$144.99	$145.00	$145.00
Purchase #3	$67.99	10.211%	$74.9325	$74.93	$74.95	$74.90
Purchase #4	$89.30	5.569%	$94.2731	$94.27	$94.25	$94.30
Purchase #5	$82.72	3.626%	$85.7194	$85.72	$85.70	$85.70
Purchase #6	$172.32	11.225%	$191.6629	$191.66	$191.65	$191.70
Purchase #7	$229.25	11.223%	$254.9787	$254.98	$255.00	$255.00
7 purchase totals =	$1,018.54		$1,108.9343	$1,108.93	$1,108.95	$1,109.00