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	$89.67	10.279%	$98.8872	$98.89	$98.90	$98.90
Purchase #2	$172.50	8.602%	$187.3385	$187.34	$187.35	$187.30
Purchase #3	$29.26	7.310%	$31.3989	$31.40	$31.40	$31.40
Purchase #4	$74.83	4.421%	$78.1382	$78.14	$78.15	$78.10
Purchase #5	$99.76	9.758%	$109.4946	$109.49	$109.50	$109.50
Purchase #6	$110.69	5.786%	$117.0945	$117.09	$117.10	$117.10
Purchase #7	$121.60	13.522%	$138.0428	$138.04	$138.05	$138.00
7 purchase totals =	$698.31		$760.3947	$760.39	$760.45	$760.30