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	$232.78	4.484%	$243.2179	$243.22	$243.20	$243.20
Purchase #2	$126.27	13.121%	$142.8379	$142.84	$142.85	$142.80
Purchase #3	$48.45	12.487%	$54.5	$54.50	$54.50	$54.50
Purchase #4	$92.46	13.155%	$104.6231	$104.62	$104.60	$104.60
Purchase #5	$202.37	13.107%	$228.8946	$228.89	$228.90	$228.90
Purchase #6	$79.48	7.482%	$85.4267	$85.43	$85.45	$85.40
Purchase #7	$106.95	6.284%	$113.6707	$113.67	$113.65	$113.70
7 purchase totals =	$888.76		$973.1709	$973.17	$973.15	$973.10