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	$180.40	5.346%	$190.0442	$190.04	$190.05	$190.00
Purchase #2	$237.84	8.244%	$257.4475	$257.45	$257.45	$257.40
Purchase #3	$133.40	13.139%	$150.9274	$150.93	$150.95	$150.90
Purchase #4	$145.46	13.755%	$165.468	$165.47	$165.45	$165.50
Purchase #5	$91.37	3.409%	$94.4848	$94.48	$94.50	$94.50
Purchase #6	$213.70	4.242%	$222.7652	$222.77	$222.75	$222.80
Purchase #7	$171.64	5.318%	$180.7678	$180.77	$180.75	$180.80
7 purchase totals =	$1,173.81		$1,261.9049	$1,261.91	$1,261.90	$1,261.90