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	$108.86	8.807%	$118.4473	$118.45	$118.45	$118.40
Purchase #2	$64.42	10.617%	$71.2595	$71.26	$71.25	$71.30
Purchase #3	$245.54	3.462%	$254.0406	$254.04	$254.05	$254.00
Purchase #4	$211.31	8.611%	$229.5059	$229.51	$229.50	$229.50
Purchase #5	$184.55	11.268%	$205.3451	$205.35	$205.35	$205.30
Purchase #6	$161.70	3.496%	$167.353	$167.35	$167.35	$167.40
Purchase #7	$98.73	11.373%	$109.9586	$109.96	$109.95	$110.00
7 purchase totals =	$1,075.11		$1,155.9100	$1,155.92	$1,155.90	$1,155.90