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	$56.30	5.556%	$59.428	$59.43	$59.45	$59.40
Purchase #2	$55.37	8.792%	$60.2381	$60.24	$60.25	$60.20
Purchase #3	$97.67	12.443%	$109.8231	$109.82	$109.80	$109.80
Purchase #4	$12.25	13.350%	$13.8854	$13.89	$13.90	$13.90
Purchase #5	$250.28	12.258%	$280.9593	$280.96	$280.95	$281.00
Purchase #6	$216.58	5.277%	$228.0089	$228.01	$228.00	$228.00
Purchase #7	$159.95	7.266%	$171.572	$171.57	$171.55	$171.60
7 purchase totals =	$848.40		$923.9148	$923.92	$923.90	$923.90