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	$207.72	13.662%	$236.0987	$236.10	$236.10	$236.10
Purchase #2	$36.88	8.763%	$40.1118	$40.11	$40.10	$40.10
Purchase #3	$215.86	9.552%	$236.4789	$236.48	$236.50	$236.50
Purchase #4	$85.53	4.610%	$89.4729	$89.47	$89.45	$89.50
Purchase #5	$155.65	9.620%	$170.6235	$170.62	$170.60	$170.60
Purchase #6	$199.84	5.744%	$211.3188	$211.32	$211.30	$211.30
Purchase #7	$107.89	4.270%	$112.4969	$112.50	$112.50	$112.50
7 purchase totals =	$1,009.37		$1,096.6015	$1,096.60	$1,096.55	$1,096.60