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	$194.87	6.469%	$207.4761	$207.48	$207.50	$207.50
Purchase #2	$193.86	6.611%	$206.6761	$206.68	$206.70	$206.70
Purchase #3	$55.67	6.465%	$59.2691	$59.27	$59.25	$59.30
Purchase #4	$18.50	12.237%	$20.7638	$20.76	$20.75	$20.80
Purchase #5	$6.90	10.462%	$7.6219	$7.62	$7.60	$7.60
Purchase #6	$134.40	10.214%	$148.1276	$148.13	$148.15	$148.10
Purchase #7	$69.97	12.244%	$78.5371	$78.54	$78.55	$78.50
7 purchase totals =	$674.17		$728.4717	$728.48	$728.50	$728.50