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	$187.46	12.490%	$210.8738	$210.87	$210.85	$210.90
Purchase #2	$162.40	7.648%	$174.8204	$174.82	$174.80	$174.80
Purchase #3	$171.35	13.680%	$194.7907	$194.79	$194.80	$194.80
Purchase #4	$52.49	9.483%	$57.4676	$57.47	$57.45	$57.50
Purchase #5	$181.60	4.368%	$189.5323	$189.53	$189.55	$189.50
Purchase #6	$171.93	4.161%	$179.084	$179.08	$179.10	$179.10
Purchase #7	$164.57	4.766%	$172.4134	$172.41	$172.40	$172.40
7 purchase totals =	$1,091.80		$1,178.9822	$1,178.97	$1,178.95	$1,179.00