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	$55.89	12.588%	$62.9254	$62.93	$62.95	$62.90
Purchase #2	$141.51	11.710%	$158.0808	$158.08	$158.10	$158.10
Purchase #3	$38.80	4.215%	$40.4354	$40.44	$40.45	$40.40
Purchase #4	$250.50	4.807%	$262.5415	$262.54	$262.55	$262.50
Purchase #5	$167.62	10.785%	$185.6978	$185.70	$185.70	$185.70
Purchase #6	$110.25	3.818%	$114.4593	$114.46	$114.45	$114.50
Purchase #7	$101.72	12.202%	$114.1319	$114.13	$114.15	$114.10
7 purchase totals =	$866.29		$938.2721	$938.28	$938.35	$938.20