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	$69.64	10.730%	$77.1124	$77.11	$77.10	$77.10
Purchase #2	$33.94	11.764%	$37.9327	$37.93	$37.95	$37.90
Purchase #3	$95.90	6.685%	$102.3109	$102.31	$102.30	$102.30
Purchase #4	$151.66	10.208%	$167.1415	$167.14	$167.15	$167.10
Purchase #5	$62.45	6.181%	$66.31	$66.31	$66.30	$66.30
Purchase #6	$51.37	10.712%	$56.8728	$56.87	$56.85	$56.90
Purchase #7	$172.52	10.447%	$190.5432	$190.54	$190.55	$190.50
7 purchase totals =	$637.48		$698.2235	$698.21	$698.20	$698.10