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	$102.85	8.503%	$111.5953	$111.60	$111.60	$111.60
Purchase #2	$165.86	9.357%	$181.3795	$181.38	$181.40	$181.40
Purchase #3	$161.88	4.761%	$169.5871	$169.59	$169.60	$169.60
Purchase #4	$176.73	6.595%	$188.3853	$188.39	$188.40	$188.40
Purchase #5	$104.44	7.809%	$112.5957	$112.60	$112.60	$112.60
Purchase #6	$189.72	12.154%	$212.7786	$212.78	$212.80	$212.80
Purchase #7	$165.47	5.281%	$174.2085	$174.21	$174.20	$174.20
7 purchase totals =	$1,066.95		$1,150.5300	$1,150.55	$1,150.60	$1,150.60