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	$140.29	6.117%	$148.8715	$148.87	$148.85	$148.90
Purchase #2	$10.41	3.548%	$10.7793	$10.78	$10.80	$10.80
Purchase #3	$120.49	9.872%	$132.3848	$132.38	$132.40	$132.40
Purchase #4	$248.38	13.131%	$280.9948	$280.99	$281.00	$281.00
Purchase #5	$55.40	7.191%	$59.3838	$59.38	$59.40	$59.40
Purchase #6	$109.66	7.112%	$117.459	$117.46	$117.45	$117.50
Purchase #7	$62.62	7.767%	$67.4837	$67.48	$67.50	$67.50
7 purchase totals =	$747.25		$817.3569	$817.34	$817.40	$817.50