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	$55.92	7.162%	$59.925	$59.93	$59.95	$59.90
Purchase #2	$32.60	8.396%	$35.3371	$35.34	$35.35	$35.30
Purchase #3	$190.72	12.846%	$215.2199	$215.22	$215.20	$215.20
Purchase #4	$39.95	13.144%	$45.201	$45.20	$45.20	$45.20
Purchase #5	$8.76	11.673%	$9.7826	$9.78	$9.80	$9.80
Purchase #6	$241.77	9.499%	$264.7357	$264.74	$264.75	$264.70
Purchase #7	$227.94	4.686%	$238.6213	$238.62	$238.60	$238.60
7 purchase totals =	$797.66		$868.8226	$868.83	$868.85	$868.70