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	$141.56	10.230%	$156.0416	$156.04	$156.05	$156.00
Purchase #2	$45.77	12.534%	$51.5068	$51.51	$51.50	$51.50
Purchase #3	$28.28	13.168%	$32.0039	$32.00	$32.00	$32.00
Purchase #4	$28.63	12.791%	$32.2921	$32.29	$32.30	$32.30
Purchase #5	$95.94	13.703%	$109.0867	$109.09	$109.10	$109.10
Purchase #6	$205.81	8.727%	$223.771	$223.77	$223.75	$223.80
Purchase #7	$118.46	8.355%	$128.3573	$128.36	$128.35	$128.40
7 purchase totals =	$664.45		$733.0594	$733.06	$733.05	$733.10