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	$64.96	11.789%	$72.6181	$72.62	$72.60	$72.60
Purchase #2	$176.47	13.798%	$200.8193	$200.82	$200.80	$200.80
Purchase #3	$162.78	13.760%	$185.1785	$185.18	$185.20	$185.20
Purchase #4	$62.28	3.813%	$64.6547	$64.65	$64.65	$64.70
Purchase #5	$58.89	5.671%	$62.2297	$62.23	$62.25	$62.20
Purchase #6	$176.38	13.605%	$200.3765	$200.38	$200.40	$200.40
Purchase #7	$73.63	9.660%	$80.7427	$80.74	$80.75	$80.70
7 purchase totals =	$775.39		$866.6195	$866.62	$866.65	$866.60