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	$59.45	6.420%	$63.2667	$63.27	$63.25	$63.30
Purchase #2	$149.81	9.794%	$164.4824	$164.48	$164.50	$164.50
Purchase #3	$65.38	4.726%	$68.4699	$68.47	$68.45	$68.50
Purchase #4	$156.76	5.428%	$165.2689	$165.27	$165.25	$165.30
Purchase #5	$188.76	6.372%	$200.7878	$200.79	$200.80	$200.80
Purchase #6	$172.93	4.856%	$181.3275	$181.33	$181.35	$181.30
Purchase #7	$54.95	8.168%	$59.4383	$59.44	$59.45	$59.40
7 purchase totals =	$848.04		$903.0415	$903.05	$903.05	$903.10