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	$150.97	10.451%	$166.7479	$166.75	$166.75	$166.70
Purchase #2	$164.57	4.476%	$171.9362	$171.94	$171.95	$171.90
Purchase #3	$95.52	6.670%	$101.8912	$101.89	$101.90	$101.90
Purchase #4	$81.26	5.134%	$85.4319	$85.43	$85.45	$85.40
Purchase #5	$189.46	12.329%	$212.8185	$212.82	$212.80	$212.80
Purchase #6	$210.56	7.833%	$227.0532	$227.05	$227.05	$227.10
Purchase #7	$196.75	9.549%	$215.5377	$215.54	$215.55	$215.50
7 purchase totals =	$1,089.09		$1,181.4166	$1,181.42	$1,181.45	$1,181.30