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	$93.78	3.811%	$97.354	$97.35	$97.35	$97.40
Purchase #2	$63.85	13.601%	$72.5342	$72.53	$72.55	$72.50
Purchase #3	$70.85	11.109%	$78.7207	$78.72	$78.70	$78.70
Purchase #4	$157.32	6.631%	$167.7519	$167.75	$167.75	$167.80
Purchase #5	$35.27	9.492%	$38.6178	$38.62	$38.60	$38.60
Purchase #6	$88.77	11.216%	$98.7264	$98.73	$98.75	$98.70
Purchase #7	$45.41	8.271%	$49.1659	$49.17	$49.15	$49.20
7 purchase totals =	$555.25		$602.8709	$602.87	$602.85	$602.90