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	$225.97	3.448%	$233.7614	$233.76	$233.75	$233.80
Purchase #2	$78.44	9.149%	$85.6165	$85.62	$85.60	$85.60
Purchase #3	$206.46	7.742%	$222.4441	$222.44	$222.45	$222.40
Purchase #4	$109.77	13.437%	$124.5198	$124.52	$124.50	$124.50
Purchase #5	$228.89	9.357%	$250.3072	$250.31	$250.30	$250.30
Purchase #6	$156.62	4.215%	$163.2215	$163.22	$163.20	$163.20
Purchase #7	$29.67	6.436%	$31.5796	$31.58	$31.60	$31.60
7 purchase totals =	$1,035.82		$1,111.4501	$1,111.45	$1,111.40	$1,111.40