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	$185.77	4.594%	$194.3043	$194.30	$194.30	$194.30
Purchase #2	$161.54	4.548%	$168.8868	$168.89	$168.90	$168.90
Purchase #3	$248.76	12.600%	$280.1038	$280.10	$280.10	$280.10
Purchase #4	$247.59	3.517%	$256.2977	$256.30	$256.30	$256.30
Purchase #5	$193.92	8.815%	$211.014	$211.01	$211.00	$211.00
Purchase #6	$162.90	9.725%	$178.742	$178.74	$178.75	$178.70
Purchase #7	$221.98	10.778%	$245.905	$245.91	$245.90	$245.90
7 purchase totals =	$1,422.46		$1,535.2536	$1,535.25	$1,535.25	$1,535.20