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	$172.37	10.175%	$189.9086	$189.91	$189.90	$189.90
Purchase #2	$168.91	7.123%	$180.9415	$180.94	$180.95	$180.90
Purchase #3	$171.95	5.606%	$181.5895	$181.59	$181.60	$181.60
Purchase #4	$97.66	7.147%	$104.6398	$104.64	$104.65	$104.60
Purchase #5	$234.84	13.243%	$265.9399	$265.94	$265.95	$265.90
Purchase #6	$30.98	5.815%	$32.7815	$32.78	$32.80	$32.80
Purchase #7	$147.73	13.862%	$168.2083	$168.21	$168.20	$168.20
7 purchase totals =	$1,024.44		$1,124.0091	$1,124.01	$1,124.05	$1,123.90