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	$136.74	10.268%	$150.7805	$150.78	$150.80	$150.80
Purchase #2	$14.54	9.262%	$15.8867	$15.89	$15.90	$15.90
Purchase #3	$248.82	8.629%	$270.2907	$270.29	$270.30	$270.30
Purchase #4	$123.73	3.120%	$127.5904	$127.59	$127.60	$127.60
Purchase #5	$183.79	12.424%	$206.6241	$206.62	$206.60	$206.60
Purchase #6	$86.87	7.403%	$93.301	$93.30	$93.30	$93.30
Purchase #7	$41.25	3.252%	$42.5915	$42.59	$42.60	$42.60
7 purchase totals =	$835.74		$907.0649	$907.06	$907.10	$907.10