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	$154.58	11.717%	$172.6921	$172.69	$172.70	$172.70
Purchase #2	$5.54	3.700%	$5.745	$5.75	$5.75	$5.70
Purchase #3	$243.79	5.150%	$256.3452	$256.35	$256.35	$256.30
Purchase #4	$97.71	5.690%	$103.2697	$103.27	$103.25	$103.30
Purchase #5	$39.54	9.297%	$43.216	$43.22	$43.20	$43.20
Purchase #6	$164.82	4.549%	$172.3177	$172.32	$172.30	$172.30
Purchase #7	$121.41	12.740%	$136.8776	$136.88	$136.90	$136.90
7 purchase totals =	$827.39		$890.4633	$890.48	$890.45	$890.40