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	$102.30	11.753%	$114.3233	$114.32	$114.30	$114.30
Purchase #2	$147.71	13.615%	$167.8207	$167.82	$167.80	$167.80
Purchase #3	$134.81	3.529%	$139.5674	$139.57	$139.55	$139.60
Purchase #4	$12.93	11.214%	$14.38	$14.38	$14.40	$14.40
Purchase #5	$198.53	11.351%	$221.0651	$221.07	$221.05	$221.10
Purchase #6	$52.86	11.836%	$59.1165	$59.12	$59.10	$59.10
Purchase #7	$246.89	3.313%	$255.0695	$255.07	$255.05	$255.10
7 purchase totals =	$896.03		$971.3425	$971.35	$971.25	$971.40