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	$88.34	11.380%	$98.3931	$98.39	$98.40	$98.40
Purchase #2	$10.90	13.214%	$12.3403	$12.34	$12.35	$12.30
Purchase #3	$129.60	7.790%	$139.6958	$139.70	$139.70	$139.70
Purchase #4	$13.72	8.564%	$14.895	$14.90	$14.90	$14.90
Purchase #5	$86.52	6.279%	$91.9526	$91.95	$91.95	$92.00
Purchase #6	$208.75	6.366%	$222.039	$222.04	$222.05	$222.00
Purchase #7	$100.76	10.201%	$111.0385	$111.04	$111.05	$111.00
7 purchase totals =	$638.59		$690.3543	$690.36	$690.40	$690.30