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	$143.33	3.703%	$148.6375	$148.64	$148.65	$148.60
Purchase #2	$250.37	3.298%	$258.6272	$258.63	$258.65	$258.60
Purchase #3	$184.72	3.315%	$190.8435	$190.84	$190.85	$190.80
Purchase #4	$112.89	4.768%	$118.2726	$118.27	$118.25	$118.30
Purchase #5	$49.80	9.655%	$54.6082	$54.61	$54.60	$54.60
Purchase #6	$191.79	7.634%	$206.4312	$206.43	$206.45	$206.40
Purchase #7	$25.32	10.533%	$27.987	$27.99	$28.00	$28.00
7 purchase totals =	$958.22		$1,005.4072	$1,005.41	$1,005.45	$1,005.30