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	$169.27	3.217%	$174.7154	$174.72	$174.70	$174.70
Purchase #2	$110.82	7.674%	$119.3243	$119.32	$119.30	$119.30
Purchase #3	$114.34	11.129%	$127.0649	$127.06	$127.05	$127.10
Purchase #4	$105.89	6.705%	$112.9899	$112.99	$113.00	$113.00
Purchase #5	$202.33	13.819%	$230.29	$230.29	$230.30	$230.30
Purchase #6	$126.70	10.161%	$139.574	$139.57	$139.55	$139.60
Purchase #7	$224.65	13.675%	$255.3709	$255.37	$255.35	$255.40
7 purchase totals =	$1,054.00		$1,159.3294	$1,159.32	$1,159.25	$1,159.40