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	$154.88	7.736%	$166.8615	$166.86	$166.85	$166.90
Purchase #2	$117.34	12.406%	$131.8972	$131.90	$131.90	$131.90
Purchase #3	$28.94	12.853%	$32.6597	$32.66	$32.65	$32.70
Purchase #4	$96.62	6.840%	$103.2288	$103.23	$103.25	$103.20
Purchase #5	$45.91	10.631%	$50.7907	$50.79	$50.80	$50.80
Purchase #6	$65.66	10.750%	$72.7185	$72.72	$72.70	$72.70
Purchase #7	$145.59	10.445%	$160.7969	$160.80	$160.80	$160.80
7 purchase totals =	$654.94		$718.9533	$718.96	$718.95	$719.00