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	$171.54	10.373%	$189.3338	$189.33	$189.35	$189.30
Purchase #2	$170.90	3.573%	$177.0063	$177.01	$177.00	$177.00
Purchase #3	$148.54	3.434%	$153.6409	$153.64	$153.65	$153.60
Purchase #4	$95.37	5.684%	$100.7908	$100.79	$100.80	$100.80
Purchase #5	$163.47	9.812%	$179.5097	$179.51	$179.50	$179.50
Purchase #6	$121.73	5.494%	$128.4178	$128.42	$128.40	$128.40
Purchase #7	$218.63	12.470%	$245.8932	$245.89	$245.90	$245.90
7 purchase totals =	$1,090.18		$1,174.5925	$1,174.59	$1,174.60	$1,174.50