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	$101.65	10.747%	$112.5743	$112.57	$112.55	$112.60
Purchase #2	$189.58	12.474%	$213.2282	$213.23	$213.25	$213.20
Purchase #3	$148.41	12.238%	$166.5724	$166.57	$166.55	$166.60
Purchase #4	$88.54	8.347%	$95.9304	$95.93	$95.95	$95.90
Purchase #5	$183.25	6.349%	$194.8845	$194.88	$194.90	$194.90
Purchase #6	$151.92	5.240%	$159.8806	$159.88	$159.90	$159.90
Purchase #7	$138.75	12.675%	$156.3366	$156.34	$156.35	$156.30
7 purchase totals =	$1,002.10		$1,099.4070	$1,099.40	$1,099.45	$1,099.40