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	$184.53	12.293%	$207.2143	$207.21	$207.20	$207.20
Purchase #2	$123.36	4.429%	$128.8236	$128.82	$128.80	$128.80
Purchase #3	$73.75	11.847%	$82.4872	$82.49	$82.50	$82.50
Purchase #4	$115.96	13.343%	$131.4325	$131.43	$131.45	$131.40
Purchase #5	$133.84	12.380%	$150.4094	$150.41	$150.40	$150.40
Purchase #6	$166.28	13.169%	$188.1774	$188.18	$188.20	$188.20
Purchase #7	$190.62	9.135%	$208.0331	$208.03	$208.05	$208.00
7 purchase totals =	$988.34		$1,096.5775	$1,096.57	$1,096.60	$1,096.50