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	$171.98	13.308%	$194.8671	$194.87	$194.85	$194.90
Purchase #2	$80.38	13.279%	$91.0537	$91.05	$91.05	$91.10
Purchase #3	$208.60	7.368%	$223.9696	$223.97	$223.95	$224.00
Purchase #4	$87.45	10.793%	$96.8885	$96.89	$96.90	$96.90
Purchase #5	$69.91	12.867%	$78.9053	$78.91	$78.90	$78.90
Purchase #6	$59.81	11.252%	$66.5398	$66.54	$66.55	$66.50
Purchase #7	$51.27	9.313%	$56.0448	$56.04	$56.05	$56.00
7 purchase totals =	$729.40		$808.2688	$808.27	$808.25	$808.30