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	$246.75	3.479%	$255.3344	$255.33	$255.35	$255.30
Purchase #2	$88.75	9.205%	$96.9194	$96.92	$96.90	$96.90
Purchase #3	$99.69	11.123%	$110.7785	$110.78	$110.80	$110.80
Purchase #4	$227.98	4.497%	$238.2323	$238.23	$238.25	$238.20
Purchase #5	$98.85	7.318%	$106.0838	$106.08	$106.10	$106.10
Purchase #6	$141.39	10.631%	$156.4212	$156.42	$156.40	$156.40
Purchase #7	$54.62	4.533%	$57.0959	$57.10	$57.10	$57.10
7 purchase totals =	$958.03		$1,020.8655	$1,020.86	$1,020.90	$1,020.80