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	$110.88	3.244%	$114.4769	$114.48	$114.50	$114.50
Purchase #2	$173.82	9.375%	$190.1156	$190.12	$190.10	$190.10
Purchase #3	$100.43	3.845%	$104.2915	$104.29	$104.30	$104.30
Purchase #4	$22.40	9.797%	$24.5945	$24.59	$24.60	$24.60
Purchase #5	$106.98	9.591%	$117.2405	$117.24	$117.25	$117.20
Purchase #6	$99.32	10.578%	$109.8261	$109.83	$109.85	$109.80
Purchase #7	$22.74	12.248%	$25.5252	$25.53	$25.55	$25.50
7 purchase totals =	$636.57		$686.0703	$686.08	$686.15	$686.00