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	$69.71	10.350%	$76.925	$76.93	$76.95	$76.90
Purchase #2	$101.36	11.230%	$112.7427	$112.74	$112.75	$112.70
Purchase #3	$45.82	10.309%	$50.5436	$50.54	$50.55	$50.50
Purchase #4	$47.94	9.140%	$52.3217	$52.32	$52.30	$52.30
Purchase #5	$73.25	13.211%	$82.9271	$82.93	$82.95	$82.90
Purchase #6	$78.48	6.357%	$83.469	$83.47	$83.45	$83.50
Purchase #7	$148.37	5.616%	$156.7025	$156.70	$156.70	$156.70
7 purchase totals =	$564.93		$615.6316	$615.63	$615.65	$615.50