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	$66.94	9.500%	$73.2993	$73.30	$73.30	$73.30
Purchase #2	$82.99	13.792%	$94.436	$94.44	$94.45	$94.40
Purchase #3	$99.79	12.536%	$112.2997	$112.30	$112.30	$112.30
Purchase #4	$158.94	12.363%	$178.5898	$178.59	$178.60	$178.60
Purchase #5	$219.33	3.802%	$227.6689	$227.67	$227.65	$227.70
Purchase #6	$83.55	9.460%	$91.4538	$91.45	$91.45	$91.50
Purchase #7	$41.34	5.728%	$43.708	$43.71	$43.70	$43.70
7 purchase totals =	$752.88		$821.4555	$821.46	$821.45	$821.50