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	$118.47	11.327%	$131.8891	$131.89	$131.90	$131.90
Purchase #2	$222.79	5.241%	$234.4664	$234.47	$234.45	$234.50
Purchase #3	$92.80	11.414%	$103.3922	$103.39	$103.40	$103.40
Purchase #4	$239.51	13.235%	$271.2091	$271.21	$271.20	$271.20
Purchase #5	$185.71	7.872%	$200.3291	$200.33	$200.35	$200.30
Purchase #6	$116.75	9.396%	$127.7198	$127.72	$127.70	$127.70
Purchase #7	$13.39	5.609%	$14.141	$14.14	$14.15	$14.10
7 purchase totals =	$989.42		$1,083.1467	$1,083.15	$1,083.15	$1,083.10