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	$171.88	10.517%	$189.9566	$189.96	$189.95	$190.00
Purchase #2	$143.26	5.139%	$150.6221	$150.62	$150.60	$150.60
Purchase #3	$52.38	3.171%	$54.041	$54.04	$54.05	$54.00
Purchase #4	$117.94	13.413%	$133.7593	$133.76	$133.75	$133.80
Purchase #5	$46.77	11.549%	$52.1715	$52.17	$52.15	$52.20
Purchase #6	$157.78	8.704%	$171.5132	$171.51	$171.50	$171.50
Purchase #7	$30.76	8.338%	$33.3248	$33.32	$33.30	$33.30
7 purchase totals =	$720.77		$785.3885	$785.38	$785.30	$785.40