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	$157.26	10.499%	$173.7707	$173.77	$173.75	$173.80
Purchase #2	$211.41	8.616%	$229.6251	$229.63	$229.65	$229.60
Purchase #3	$235.83	4.246%	$245.8433	$245.84	$245.85	$245.80
Purchase #4	$227.69	12.796%	$256.8252	$256.83	$256.85	$256.80
Purchase #5	$154.56	5.171%	$162.5523	$162.55	$162.55	$162.60
Purchase #6	$128.73	6.813%	$137.5004	$137.50	$137.50	$137.50
Purchase #7	$11.89	13.377%	$13.4805	$13.48	$13.50	$13.50
7 purchase totals =	$1,127.37		$1,219.5975	$1,219.60	$1,219.65	$1,219.60