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	$118.55	6.385%	$126.1194	$126.12	$126.10	$126.10
Purchase #2	$77.70	13.522%	$88.2066	$88.21	$88.20	$88.20
Purchase #3	$35.40	11.127%	$39.339	$39.34	$39.35	$39.30
Purchase #4	$114.89	11.171%	$127.7244	$127.72	$127.70	$127.70
Purchase #5	$193.61	13.351%	$219.4589	$219.46	$219.45	$219.50
Purchase #6	$70.77	10.458%	$78.1711	$78.17	$78.15	$78.20
Purchase #7	$229.57	8.705%	$249.5541	$249.55	$249.55	$249.60
7 purchase totals =	$840.49		$928.5735	$928.57	$928.50	$928.60