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	$159.72	4.595%	$167.0591	$167.06	$167.05	$167.10
Purchase #2	$138.47	10.118%	$152.4804	$152.48	$152.50	$152.50
Purchase #3	$181.62	3.870%	$188.6487	$188.65	$188.65	$188.60
Purchase #4	$85.33	4.338%	$89.0316	$89.03	$89.05	$89.00
Purchase #5	$118.31	6.583%	$126.0983	$126.10	$126.10	$126.10
Purchase #6	$164.60	6.234%	$174.8612	$174.86	$174.85	$174.90
Purchase #7	$39.64	12.621%	$44.643	$44.64	$44.65	$44.60
7 purchase totals =	$887.69		$942.8223	$942.82	$942.85	$942.80