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	$222.60	11.143%	$247.4043	$247.40	$247.40	$247.40
Purchase #2	$38.88	11.156%	$43.2175	$43.22	$43.20	$43.20
Purchase #3	$68.96	3.353%	$71.2722	$71.27	$71.25	$71.30
Purchase #4	$55.54	12.141%	$62.2831	$62.28	$62.30	$62.30
Purchase #5	$58.29	3.403%	$60.2736	$60.27	$60.25	$60.30
Purchase #6	$193.50	10.391%	$213.6066	$213.61	$213.60	$213.60
Purchase #7	$39.53	10.239%	$43.5775	$43.58	$43.60	$43.60
7 purchase totals =	$677.30		$741.6348	$741.63	$741.60	$741.70