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	$31.66	5.171%	$33.2971	$33.30	$33.30	$33.30
Purchase #2	$231.42	10.400%	$255.4877	$255.49	$255.50	$255.50
Purchase #3	$206.96	3.607%	$214.425	$214.43	$214.45	$214.40
Purchase #4	$180.71	5.212%	$190.1286	$190.13	$190.15	$190.10
Purchase #5	$86.62	4.152%	$90.2165	$90.22	$90.20	$90.20
Purchase #6	$169.80	5.211%	$178.6483	$178.65	$178.65	$178.60
Purchase #7	$73.89	3.403%	$76.4045	$76.40	$76.40	$76.40
7 purchase totals =	$981.06		$1,038.6077	$1,038.62	$1,038.65	$1,038.50