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	$113.37	4.383%	$118.339	$118.34	$118.35	$118.30
Purchase #2	$160.89	11.843%	$179.9442	$179.94	$179.95	$179.90
Purchase #3	$86.27	4.745%	$90.3635	$90.36	$90.35	$90.40
Purchase #4	$80.68	10.809%	$89.4007	$89.40	$89.40	$89.40
Purchase #5	$235.83	8.111%	$254.9582	$254.96	$254.95	$255.00
Purchase #6	$67.47	3.273%	$69.6783	$69.68	$69.70	$69.70
Purchase #7	$229.76	3.170%	$237.0434	$237.04	$237.05	$237.00
7 purchase totals =	$974.27		$1,039.7273	$1,039.72	$1,039.75	$1,039.70